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41eecbd712
TCP can transform a TIMEWAIT socket into a SYN_RECV one from a SYN packet, and the ISN of the SYNACK packet is normally generated using TIMEWAIT tw_snd_nxt : tcp_timewait_state_process() ... u32 isn = tcptw->tw_snd_nxt + 65535 + 2; if (isn == 0) isn++; TCP_SKB_CB(skb)->tcp_tw_isn = isn; return TCP_TW_SYN; This SYN packet also bypasses normal checks against listen queue being full or not. tcp_conn_request() ... __u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn; ... /* TW buckets are converted to open requests without * limitations, they conserve resources and peer is * evidently real one. */ if ((syncookies == 2 || inet_csk_reqsk_queue_is_full(sk)) && !isn) { want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name); if (!want_cookie) goto drop; } This was using TCP_SKB_CB(skb)->tcp_tw_isn field in skb. Unfortunately this field has been accidentally cleared after the call to tcp_timewait_state_process() returning TCP_TW_SYN. Using a field in TCP_SKB_CB(skb) for a temporary state is overkill. Switch instead to a per-cpu variable. As a bonus, we do not have to clear tcp_tw_isn in TCP receive fast path. It is temporarily set then cleared only in the TCP_TW_SYN dance. Fixes:4ad19de877
("net: tcp6: fix double call of tcp_v6_fill_cb()") Fixes:eeea10b83a
("tcp: add tcp_v4_fill_cb()/tcp_v4_restore_cb()") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
939 lines
29 KiB
C
939 lines
29 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Implementation of the Transmission Control Protocol(TCP).
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Mark Evans, <evansmp@uhura.aston.ac.uk>
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* Corey Minyard <wf-rch!minyard@relay.EU.net>
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* Florian La Roche, <flla@stud.uni-sb.de>
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* Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
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* Linus Torvalds, <torvalds@cs.helsinki.fi>
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* Alan Cox, <gw4pts@gw4pts.ampr.org>
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* Matthew Dillon, <dillon@apollo.west.oic.com>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Jorge Cwik, <jorge@laser.satlink.net>
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*/
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#include <net/tcp.h>
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#include <net/xfrm.h>
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#include <net/busy_poll.h>
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static bool tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
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{
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if (seq == s_win)
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return true;
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if (after(end_seq, s_win) && before(seq, e_win))
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return true;
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return seq == e_win && seq == end_seq;
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}
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static enum tcp_tw_status
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tcp_timewait_check_oow_rate_limit(struct inet_timewait_sock *tw,
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const struct sk_buff *skb, int mib_idx)
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{
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struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
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if (!tcp_oow_rate_limited(twsk_net(tw), skb, mib_idx,
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&tcptw->tw_last_oow_ack_time)) {
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/* Send ACK. Note, we do not put the bucket,
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* it will be released by caller.
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*/
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return TCP_TW_ACK;
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}
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/* We are rate-limiting, so just release the tw sock and drop skb. */
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inet_twsk_put(tw);
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return TCP_TW_SUCCESS;
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}
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static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq)
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{
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#ifdef CONFIG_TCP_AO
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struct tcp_ao_info *ao;
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ao = rcu_dereference(tcptw->ao_info);
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if (unlikely(ao && seq < tcptw->tw_rcv_nxt))
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WRITE_ONCE(ao->rcv_sne, ao->rcv_sne + 1);
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#endif
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tcptw->tw_rcv_nxt = seq;
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}
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/*
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* * Main purpose of TIME-WAIT state is to close connection gracefully,
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* when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
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* (and, probably, tail of data) and one or more our ACKs are lost.
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* * What is TIME-WAIT timeout? It is associated with maximal packet
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* lifetime in the internet, which results in wrong conclusion, that
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* it is set to catch "old duplicate segments" wandering out of their path.
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* It is not quite correct. This timeout is calculated so that it exceeds
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* maximal retransmission timeout enough to allow to lose one (or more)
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* segments sent by peer and our ACKs. This time may be calculated from RTO.
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* * When TIME-WAIT socket receives RST, it means that another end
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* finally closed and we are allowed to kill TIME-WAIT too.
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* * Second purpose of TIME-WAIT is catching old duplicate segments.
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* Well, certainly it is pure paranoia, but if we load TIME-WAIT
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* with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
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* * If we invented some more clever way to catch duplicates
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* (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
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*
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* The algorithm below is based on FORMAL INTERPRETATION of RFCs.
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* When you compare it to RFCs, please, read section SEGMENT ARRIVES
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* from the very beginning.
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*
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* NOTE. With recycling (and later with fin-wait-2) TW bucket
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* is _not_ stateless. It means, that strictly speaking we must
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* spinlock it. I do not want! Well, probability of misbehaviour
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* is ridiculously low and, seems, we could use some mb() tricks
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* to avoid misread sequence numbers, states etc. --ANK
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*
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* We don't need to initialize tmp_out.sack_ok as we don't use the results
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*/
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enum tcp_tw_status
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tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
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const struct tcphdr *th, u32 *tw_isn)
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{
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struct tcp_options_received tmp_opt;
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struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
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bool paws_reject = false;
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tmp_opt.saw_tstamp = 0;
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if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
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tcp_parse_options(twsk_net(tw), skb, &tmp_opt, 0, NULL);
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if (tmp_opt.saw_tstamp) {
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if (tmp_opt.rcv_tsecr)
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tmp_opt.rcv_tsecr -= tcptw->tw_ts_offset;
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tmp_opt.ts_recent = tcptw->tw_ts_recent;
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tmp_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
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paws_reject = tcp_paws_reject(&tmp_opt, th->rst);
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}
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}
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if (tw->tw_substate == TCP_FIN_WAIT2) {
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/* Just repeat all the checks of tcp_rcv_state_process() */
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/* Out of window, send ACK */
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if (paws_reject ||
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!tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
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tcptw->tw_rcv_nxt,
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tcptw->tw_rcv_nxt + tcptw->tw_rcv_wnd))
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return tcp_timewait_check_oow_rate_limit(
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tw, skb, LINUX_MIB_TCPACKSKIPPEDFINWAIT2);
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if (th->rst)
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goto kill;
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if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt))
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return TCP_TW_RST;
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/* Dup ACK? */
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if (!th->ack ||
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!after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) ||
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TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
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inet_twsk_put(tw);
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return TCP_TW_SUCCESS;
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}
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/* New data or FIN. If new data arrive after half-duplex close,
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* reset.
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*/
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if (!th->fin ||
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TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1)
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return TCP_TW_RST;
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/* FIN arrived, enter true time-wait state. */
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tw->tw_substate = TCP_TIME_WAIT;
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twsk_rcv_nxt_update(tcptw, TCP_SKB_CB(skb)->end_seq);
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if (tmp_opt.saw_tstamp) {
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tcptw->tw_ts_recent_stamp = ktime_get_seconds();
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tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
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}
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inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
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return TCP_TW_ACK;
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}
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/*
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* Now real TIME-WAIT state.
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*
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* RFC 1122:
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* "When a connection is [...] on TIME-WAIT state [...]
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* [a TCP] MAY accept a new SYN from the remote TCP to
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* reopen the connection directly, if it:
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*
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* (1) assigns its initial sequence number for the new
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* connection to be larger than the largest sequence
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* number it used on the previous connection incarnation,
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* and
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*
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* (2) returns to TIME-WAIT state if the SYN turns out
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* to be an old duplicate".
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*/
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if (!paws_reject &&
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(TCP_SKB_CB(skb)->seq == tcptw->tw_rcv_nxt &&
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(TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
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/* In window segment, it may be only reset or bare ack. */
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if (th->rst) {
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/* This is TIME_WAIT assassination, in two flavors.
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* Oh well... nobody has a sufficient solution to this
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* protocol bug yet.
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*/
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if (!READ_ONCE(twsk_net(tw)->ipv4.sysctl_tcp_rfc1337)) {
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kill:
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inet_twsk_deschedule_put(tw);
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return TCP_TW_SUCCESS;
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}
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} else {
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inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
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}
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if (tmp_opt.saw_tstamp) {
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tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
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tcptw->tw_ts_recent_stamp = ktime_get_seconds();
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}
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inet_twsk_put(tw);
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return TCP_TW_SUCCESS;
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}
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/* Out of window segment.
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All the segments are ACKed immediately.
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The only exception is new SYN. We accept it, if it is
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not old duplicate and we are not in danger to be killed
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by delayed old duplicates. RFC check is that it has
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newer sequence number works at rates <40Mbit/sec.
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However, if paws works, it is reliable AND even more,
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we even may relax silly seq space cutoff.
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RED-PEN: we violate main RFC requirement, if this SYN will appear
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old duplicate (i.e. we receive RST in reply to SYN-ACK),
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we must return socket to time-wait state. It is not good,
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but not fatal yet.
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*/
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if (th->syn && !th->rst && !th->ack && !paws_reject &&
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(after(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt) ||
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(tmp_opt.saw_tstamp &&
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(s32)(tcptw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) {
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u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
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if (isn == 0)
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isn++;
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*tw_isn = isn;
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return TCP_TW_SYN;
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}
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if (paws_reject)
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__NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED);
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if (!th->rst) {
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/* In this case we must reset the TIMEWAIT timer.
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*
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* If it is ACKless SYN it may be both old duplicate
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* and new good SYN with random sequence number <rcv_nxt.
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* Do not reschedule in the last case.
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*/
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if (paws_reject || th->ack)
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inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
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return tcp_timewait_check_oow_rate_limit(
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tw, skb, LINUX_MIB_TCPACKSKIPPEDTIMEWAIT);
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}
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inet_twsk_put(tw);
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return TCP_TW_SUCCESS;
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}
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EXPORT_SYMBOL(tcp_timewait_state_process);
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static void tcp_time_wait_init(struct sock *sk, struct tcp_timewait_sock *tcptw)
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{
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#ifdef CONFIG_TCP_MD5SIG
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const struct tcp_sock *tp = tcp_sk(sk);
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struct tcp_md5sig_key *key;
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/*
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* The timewait bucket does not have the key DB from the
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* sock structure. We just make a quick copy of the
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* md5 key being used (if indeed we are using one)
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* so the timewait ack generating code has the key.
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*/
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tcptw->tw_md5_key = NULL;
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if (!static_branch_unlikely(&tcp_md5_needed.key))
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return;
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key = tp->af_specific->md5_lookup(sk, sk);
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if (key) {
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tcptw->tw_md5_key = kmemdup(key, sizeof(*key), GFP_ATOMIC);
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if (!tcptw->tw_md5_key)
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return;
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if (!static_key_fast_inc_not_disabled(&tcp_md5_needed.key.key))
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goto out_free;
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tcp_md5_add_sigpool();
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}
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return;
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out_free:
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WARN_ON_ONCE(1);
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kfree(tcptw->tw_md5_key);
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tcptw->tw_md5_key = NULL;
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#endif
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}
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/*
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* Move a socket to time-wait or dead fin-wait-2 state.
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*/
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void tcp_time_wait(struct sock *sk, int state, int timeo)
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{
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const struct inet_connection_sock *icsk = inet_csk(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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struct net *net = sock_net(sk);
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struct inet_timewait_sock *tw;
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tw = inet_twsk_alloc(sk, &net->ipv4.tcp_death_row, state);
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if (tw) {
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struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
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const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
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tw->tw_transparent = inet_test_bit(TRANSPARENT, sk);
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tw->tw_mark = sk->sk_mark;
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tw->tw_priority = READ_ONCE(sk->sk_priority);
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tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale;
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tcptw->tw_rcv_nxt = tp->rcv_nxt;
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tcptw->tw_snd_nxt = tp->snd_nxt;
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tcptw->tw_rcv_wnd = tcp_receive_window(tp);
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tcptw->tw_ts_recent = tp->rx_opt.ts_recent;
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tcptw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
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tcptw->tw_ts_offset = tp->tsoffset;
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tw->tw_usec_ts = tp->tcp_usec_ts;
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tcptw->tw_last_oow_ack_time = 0;
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tcptw->tw_tx_delay = tp->tcp_tx_delay;
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tw->tw_txhash = sk->sk_txhash;
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#if IS_ENABLED(CONFIG_IPV6)
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if (tw->tw_family == PF_INET6) {
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struct ipv6_pinfo *np = inet6_sk(sk);
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tw->tw_v6_daddr = sk->sk_v6_daddr;
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tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
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tw->tw_tclass = np->tclass;
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tw->tw_flowlabel = be32_to_cpu(np->flow_label & IPV6_FLOWLABEL_MASK);
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tw->tw_ipv6only = sk->sk_ipv6only;
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}
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#endif
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tcp_time_wait_init(sk, tcptw);
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tcp_ao_time_wait(tcptw, tp);
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/* Get the TIME_WAIT timeout firing. */
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if (timeo < rto)
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timeo = rto;
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if (state == TCP_TIME_WAIT)
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timeo = TCP_TIMEWAIT_LEN;
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/* tw_timer is pinned, so we need to make sure BH are disabled
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* in following section, otherwise timer handler could run before
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* we complete the initialization.
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*/
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local_bh_disable();
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inet_twsk_schedule(tw, timeo);
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/* Linkage updates.
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* Note that access to tw after this point is illegal.
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*/
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inet_twsk_hashdance(tw, sk, net->ipv4.tcp_death_row.hashinfo);
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local_bh_enable();
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} else {
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/* Sorry, if we're out of memory, just CLOSE this
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* socket up. We've got bigger problems than
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* non-graceful socket closings.
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*/
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NET_INC_STATS(net, LINUX_MIB_TCPTIMEWAITOVERFLOW);
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}
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tcp_update_metrics(sk);
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tcp_done(sk);
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}
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EXPORT_SYMBOL(tcp_time_wait);
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#ifdef CONFIG_TCP_MD5SIG
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static void tcp_md5_twsk_free_rcu(struct rcu_head *head)
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{
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struct tcp_md5sig_key *key;
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key = container_of(head, struct tcp_md5sig_key, rcu);
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kfree(key);
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static_branch_slow_dec_deferred(&tcp_md5_needed);
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tcp_md5_release_sigpool();
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}
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#endif
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void tcp_twsk_destructor(struct sock *sk)
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{
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#ifdef CONFIG_TCP_MD5SIG
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if (static_branch_unlikely(&tcp_md5_needed.key)) {
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struct tcp_timewait_sock *twsk = tcp_twsk(sk);
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if (twsk->tw_md5_key)
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call_rcu(&twsk->tw_md5_key->rcu, tcp_md5_twsk_free_rcu);
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}
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#endif
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tcp_ao_destroy_sock(sk, true);
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}
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EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
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void tcp_twsk_purge(struct list_head *net_exit_list)
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{
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bool purged_once = false;
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struct net *net;
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list_for_each_entry(net, net_exit_list, exit_list) {
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if (net->ipv4.tcp_death_row.hashinfo->pernet) {
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/* Even if tw_refcount == 1, we must clean up kernel reqsk */
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inet_twsk_purge(net->ipv4.tcp_death_row.hashinfo);
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} else if (!purged_once) {
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inet_twsk_purge(&tcp_hashinfo);
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purged_once = true;
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}
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}
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}
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EXPORT_SYMBOL_GPL(tcp_twsk_purge);
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|
/* Warning : This function is called without sk_listener being locked.
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|
* Be sure to read socket fields once, as their value could change under us.
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|
*/
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|
void tcp_openreq_init_rwin(struct request_sock *req,
|
|
const struct sock *sk_listener,
|
|
const struct dst_entry *dst)
|
|
{
|
|
struct inet_request_sock *ireq = inet_rsk(req);
|
|
const struct tcp_sock *tp = tcp_sk(sk_listener);
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|
int full_space = tcp_full_space(sk_listener);
|
|
u32 window_clamp;
|
|
__u8 rcv_wscale;
|
|
u32 rcv_wnd;
|
|
int mss;
|
|
|
|
mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
|
|
window_clamp = READ_ONCE(tp->window_clamp);
|
|
/* Set this up on the first call only */
|
|
req->rsk_window_clamp = window_clamp ? : dst_metric(dst, RTAX_WINDOW);
|
|
|
|
/* limit the window selection if the user enforce a smaller rx buffer */
|
|
if (sk_listener->sk_userlocks & SOCK_RCVBUF_LOCK &&
|
|
(req->rsk_window_clamp > full_space || req->rsk_window_clamp == 0))
|
|
req->rsk_window_clamp = full_space;
|
|
|
|
rcv_wnd = tcp_rwnd_init_bpf((struct sock *)req);
|
|
if (rcv_wnd == 0)
|
|
rcv_wnd = dst_metric(dst, RTAX_INITRWND);
|
|
else if (full_space < rcv_wnd * mss)
|
|
full_space = rcv_wnd * mss;
|
|
|
|
/* tcp_full_space because it is guaranteed to be the first packet */
|
|
tcp_select_initial_window(sk_listener, full_space,
|
|
mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
|
|
&req->rsk_rcv_wnd,
|
|
&req->rsk_window_clamp,
|
|
ireq->wscale_ok,
|
|
&rcv_wscale,
|
|
rcv_wnd);
|
|
ireq->rcv_wscale = rcv_wscale;
|
|
}
|
|
EXPORT_SYMBOL(tcp_openreq_init_rwin);
|
|
|
|
static void tcp_ecn_openreq_child(struct tcp_sock *tp,
|
|
const struct request_sock *req)
|
|
{
|
|
tp->ecn_flags = inet_rsk(req)->ecn_ok ? TCP_ECN_OK : 0;
|
|
}
|
|
|
|
void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
|
|
bool ca_got_dst = false;
|
|
|
|
if (ca_key != TCP_CA_UNSPEC) {
|
|
const struct tcp_congestion_ops *ca;
|
|
|
|
rcu_read_lock();
|
|
ca = tcp_ca_find_key(ca_key);
|
|
if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
|
|
icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
|
|
icsk->icsk_ca_ops = ca;
|
|
ca_got_dst = true;
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/* If no valid choice made yet, assign current system default ca. */
|
|
if (!ca_got_dst &&
|
|
(!icsk->icsk_ca_setsockopt ||
|
|
!bpf_try_module_get(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner)))
|
|
tcp_assign_congestion_control(sk);
|
|
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
}
|
|
EXPORT_SYMBOL_GPL(tcp_ca_openreq_child);
|
|
|
|
static void smc_check_reset_syn_req(const struct tcp_sock *oldtp,
|
|
struct request_sock *req,
|
|
struct tcp_sock *newtp)
|
|
{
|
|
#if IS_ENABLED(CONFIG_SMC)
|
|
struct inet_request_sock *ireq;
|
|
|
|
if (static_branch_unlikely(&tcp_have_smc)) {
|
|
ireq = inet_rsk(req);
|
|
if (oldtp->syn_smc && !ireq->smc_ok)
|
|
newtp->syn_smc = 0;
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/* This is not only more efficient than what we used to do, it eliminates
|
|
* a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
|
|
*
|
|
* Actually, we could lots of memory writes here. tp of listening
|
|
* socket contains all necessary default parameters.
|
|
*/
|
|
struct sock *tcp_create_openreq_child(const struct sock *sk,
|
|
struct request_sock *req,
|
|
struct sk_buff *skb)
|
|
{
|
|
struct sock *newsk = inet_csk_clone_lock(sk, req, GFP_ATOMIC);
|
|
const struct inet_request_sock *ireq = inet_rsk(req);
|
|
struct tcp_request_sock *treq = tcp_rsk(req);
|
|
struct inet_connection_sock *newicsk;
|
|
const struct tcp_sock *oldtp;
|
|
struct tcp_sock *newtp;
|
|
u32 seq;
|
|
#ifdef CONFIG_TCP_AO
|
|
struct tcp_ao_key *ao_key;
|
|
#endif
|
|
|
|
if (!newsk)
|
|
return NULL;
|
|
|
|
newicsk = inet_csk(newsk);
|
|
newtp = tcp_sk(newsk);
|
|
oldtp = tcp_sk(sk);
|
|
|
|
smc_check_reset_syn_req(oldtp, req, newtp);
|
|
|
|
/* Now setup tcp_sock */
|
|
newtp->pred_flags = 0;
|
|
|
|
seq = treq->rcv_isn + 1;
|
|
newtp->rcv_wup = seq;
|
|
WRITE_ONCE(newtp->copied_seq, seq);
|
|
WRITE_ONCE(newtp->rcv_nxt, seq);
|
|
newtp->segs_in = 1;
|
|
|
|
seq = treq->snt_isn + 1;
|
|
newtp->snd_sml = newtp->snd_una = seq;
|
|
WRITE_ONCE(newtp->snd_nxt, seq);
|
|
newtp->snd_up = seq;
|
|
|
|
INIT_LIST_HEAD(&newtp->tsq_node);
|
|
INIT_LIST_HEAD(&newtp->tsorted_sent_queue);
|
|
|
|
tcp_init_wl(newtp, treq->rcv_isn);
|
|
|
|
minmax_reset(&newtp->rtt_min, tcp_jiffies32, ~0U);
|
|
newicsk->icsk_ack.lrcvtime = tcp_jiffies32;
|
|
|
|
newtp->lsndtime = tcp_jiffies32;
|
|
newsk->sk_txhash = READ_ONCE(treq->txhash);
|
|
newtp->total_retrans = req->num_retrans;
|
|
|
|
tcp_init_xmit_timers(newsk);
|
|
WRITE_ONCE(newtp->write_seq, newtp->pushed_seq = treq->snt_isn + 1);
|
|
|
|
if (sock_flag(newsk, SOCK_KEEPOPEN))
|
|
inet_csk_reset_keepalive_timer(newsk,
|
|
keepalive_time_when(newtp));
|
|
|
|
newtp->rx_opt.tstamp_ok = ireq->tstamp_ok;
|
|
newtp->rx_opt.sack_ok = ireq->sack_ok;
|
|
newtp->window_clamp = req->rsk_window_clamp;
|
|
newtp->rcv_ssthresh = req->rsk_rcv_wnd;
|
|
newtp->rcv_wnd = req->rsk_rcv_wnd;
|
|
newtp->rx_opt.wscale_ok = ireq->wscale_ok;
|
|
if (newtp->rx_opt.wscale_ok) {
|
|
newtp->rx_opt.snd_wscale = ireq->snd_wscale;
|
|
newtp->rx_opt.rcv_wscale = ireq->rcv_wscale;
|
|
} else {
|
|
newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0;
|
|
newtp->window_clamp = min(newtp->window_clamp, 65535U);
|
|
}
|
|
newtp->snd_wnd = ntohs(tcp_hdr(skb)->window) << newtp->rx_opt.snd_wscale;
|
|
newtp->max_window = newtp->snd_wnd;
|
|
|
|
if (newtp->rx_opt.tstamp_ok) {
|
|
newtp->tcp_usec_ts = treq->req_usec_ts;
|
|
newtp->rx_opt.ts_recent = READ_ONCE(req->ts_recent);
|
|
newtp->rx_opt.ts_recent_stamp = ktime_get_seconds();
|
|
newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
|
|
} else {
|
|
newtp->tcp_usec_ts = 0;
|
|
newtp->rx_opt.ts_recent_stamp = 0;
|
|
newtp->tcp_header_len = sizeof(struct tcphdr);
|
|
}
|
|
if (req->num_timeout) {
|
|
newtp->total_rto = req->num_timeout;
|
|
newtp->undo_marker = treq->snt_isn;
|
|
if (newtp->tcp_usec_ts) {
|
|
newtp->retrans_stamp = treq->snt_synack;
|
|
newtp->total_rto_time = (u32)(tcp_clock_us() -
|
|
newtp->retrans_stamp) / USEC_PER_MSEC;
|
|
} else {
|
|
newtp->retrans_stamp = div_u64(treq->snt_synack,
|
|
USEC_PER_SEC / TCP_TS_HZ);
|
|
newtp->total_rto_time = tcp_clock_ms() -
|
|
newtp->retrans_stamp;
|
|
}
|
|
newtp->total_rto_recoveries = 1;
|
|
}
|
|
newtp->tsoffset = treq->ts_off;
|
|
#ifdef CONFIG_TCP_MD5SIG
|
|
newtp->md5sig_info = NULL; /*XXX*/
|
|
#endif
|
|
#ifdef CONFIG_TCP_AO
|
|
newtp->ao_info = NULL;
|
|
ao_key = treq->af_specific->ao_lookup(sk, req,
|
|
tcp_rsk(req)->ao_keyid, -1);
|
|
if (ao_key)
|
|
newtp->tcp_header_len += tcp_ao_len_aligned(ao_key);
|
|
#endif
|
|
if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len)
|
|
newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;
|
|
newtp->rx_opt.mss_clamp = req->mss;
|
|
tcp_ecn_openreq_child(newtp, req);
|
|
newtp->fastopen_req = NULL;
|
|
RCU_INIT_POINTER(newtp->fastopen_rsk, NULL);
|
|
|
|
newtp->bpf_chg_cc_inprogress = 0;
|
|
tcp_bpf_clone(sk, newsk);
|
|
|
|
__TCP_INC_STATS(sock_net(sk), TCP_MIB_PASSIVEOPENS);
|
|
|
|
return newsk;
|
|
}
|
|
EXPORT_SYMBOL(tcp_create_openreq_child);
|
|
|
|
/*
|
|
* Process an incoming packet for SYN_RECV sockets represented as a
|
|
* request_sock. Normally sk is the listener socket but for TFO it
|
|
* points to the child socket.
|
|
*
|
|
* XXX (TFO) - The current impl contains a special check for ack
|
|
* validation and inside tcp_v4_reqsk_send_ack(). Can we do better?
|
|
*
|
|
* We don't need to initialize tmp_opt.sack_ok as we don't use the results
|
|
*
|
|
* Note: If @fastopen is true, this can be called from process context.
|
|
* Otherwise, this is from BH context.
|
|
*/
|
|
|
|
struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
|
|
struct request_sock *req,
|
|
bool fastopen, bool *req_stolen)
|
|
{
|
|
struct tcp_options_received tmp_opt;
|
|
struct sock *child;
|
|
const struct tcphdr *th = tcp_hdr(skb);
|
|
__be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
|
|
bool paws_reject = false;
|
|
bool own_req;
|
|
|
|
tmp_opt.saw_tstamp = 0;
|
|
if (th->doff > (sizeof(struct tcphdr)>>2)) {
|
|
tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0, NULL);
|
|
|
|
if (tmp_opt.saw_tstamp) {
|
|
tmp_opt.ts_recent = READ_ONCE(req->ts_recent);
|
|
if (tmp_opt.rcv_tsecr)
|
|
tmp_opt.rcv_tsecr -= tcp_rsk(req)->ts_off;
|
|
/* We do not store true stamp, but it is not required,
|
|
* it can be estimated (approximately)
|
|
* from another data.
|
|
*/
|
|
tmp_opt.ts_recent_stamp = ktime_get_seconds() - reqsk_timeout(req, TCP_RTO_MAX) / HZ;
|
|
paws_reject = tcp_paws_reject(&tmp_opt, th->rst);
|
|
}
|
|
}
|
|
|
|
/* Check for pure retransmitted SYN. */
|
|
if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn &&
|
|
flg == TCP_FLAG_SYN &&
|
|
!paws_reject) {
|
|
/*
|
|
* RFC793 draws (Incorrectly! It was fixed in RFC1122)
|
|
* this case on figure 6 and figure 8, but formal
|
|
* protocol description says NOTHING.
|
|
* To be more exact, it says that we should send ACK,
|
|
* because this segment (at least, if it has no data)
|
|
* is out of window.
|
|
*
|
|
* CONCLUSION: RFC793 (even with RFC1122) DOES NOT
|
|
* describe SYN-RECV state. All the description
|
|
* is wrong, we cannot believe to it and should
|
|
* rely only on common sense and implementation
|
|
* experience.
|
|
*
|
|
* Enforce "SYN-ACK" according to figure 8, figure 6
|
|
* of RFC793, fixed by RFC1122.
|
|
*
|
|
* Note that even if there is new data in the SYN packet
|
|
* they will be thrown away too.
|
|
*
|
|
* Reset timer after retransmitting SYNACK, similar to
|
|
* the idea of fast retransmit in recovery.
|
|
*/
|
|
if (!tcp_oow_rate_limited(sock_net(sk), skb,
|
|
LINUX_MIB_TCPACKSKIPPEDSYNRECV,
|
|
&tcp_rsk(req)->last_oow_ack_time) &&
|
|
|
|
!inet_rtx_syn_ack(sk, req)) {
|
|
unsigned long expires = jiffies;
|
|
|
|
expires += reqsk_timeout(req, TCP_RTO_MAX);
|
|
if (!fastopen)
|
|
mod_timer_pending(&req->rsk_timer, expires);
|
|
else
|
|
req->rsk_timer.expires = expires;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/* Further reproduces section "SEGMENT ARRIVES"
|
|
for state SYN-RECEIVED of RFC793.
|
|
It is broken, however, it does not work only
|
|
when SYNs are crossed.
|
|
|
|
You would think that SYN crossing is impossible here, since
|
|
we should have a SYN_SENT socket (from connect()) on our end,
|
|
but this is not true if the crossed SYNs were sent to both
|
|
ends by a malicious third party. We must defend against this,
|
|
and to do that we first verify the ACK (as per RFC793, page
|
|
36) and reset if it is invalid. Is this a true full defense?
|
|
To convince ourselves, let us consider a way in which the ACK
|
|
test can still pass in this 'malicious crossed SYNs' case.
|
|
Malicious sender sends identical SYNs (and thus identical sequence
|
|
numbers) to both A and B:
|
|
|
|
A: gets SYN, seq=7
|
|
B: gets SYN, seq=7
|
|
|
|
By our good fortune, both A and B select the same initial
|
|
send sequence number of seven :-)
|
|
|
|
A: sends SYN|ACK, seq=7, ack_seq=8
|
|
B: sends SYN|ACK, seq=7, ack_seq=8
|
|
|
|
So we are now A eating this SYN|ACK, ACK test passes. So
|
|
does sequence test, SYN is truncated, and thus we consider
|
|
it a bare ACK.
|
|
|
|
If icsk->icsk_accept_queue.rskq_defer_accept, we silently drop this
|
|
bare ACK. Otherwise, we create an established connection. Both
|
|
ends (listening sockets) accept the new incoming connection and try
|
|
to talk to each other. 8-)
|
|
|
|
Note: This case is both harmless, and rare. Possibility is about the
|
|
same as us discovering intelligent life on another plant tomorrow.
|
|
|
|
But generally, we should (RFC lies!) to accept ACK
|
|
from SYNACK both here and in tcp_rcv_state_process().
|
|
tcp_rcv_state_process() does not, hence, we do not too.
|
|
|
|
Note that the case is absolutely generic:
|
|
we cannot optimize anything here without
|
|
violating protocol. All the checks must be made
|
|
before attempt to create socket.
|
|
*/
|
|
|
|
/* RFC793 page 36: "If the connection is in any non-synchronized state ...
|
|
* and the incoming segment acknowledges something not yet
|
|
* sent (the segment carries an unacceptable ACK) ...
|
|
* a reset is sent."
|
|
*
|
|
* Invalid ACK: reset will be sent by listening socket.
|
|
* Note that the ACK validity check for a Fast Open socket is done
|
|
* elsewhere and is checked directly against the child socket rather
|
|
* than req because user data may have been sent out.
|
|
*/
|
|
if ((flg & TCP_FLAG_ACK) && !fastopen &&
|
|
(TCP_SKB_CB(skb)->ack_seq !=
|
|
tcp_rsk(req)->snt_isn + 1))
|
|
return sk;
|
|
|
|
/* Also, it would be not so bad idea to check rcv_tsecr, which
|
|
* is essentially ACK extension and too early or too late values
|
|
* should cause reset in unsynchronized states.
|
|
*/
|
|
|
|
/* RFC793: "first check sequence number". */
|
|
|
|
if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
|
|
tcp_rsk(req)->rcv_nxt, tcp_rsk(req)->rcv_nxt + req->rsk_rcv_wnd)) {
|
|
/* Out of window: send ACK and drop. */
|
|
if (!(flg & TCP_FLAG_RST) &&
|
|
!tcp_oow_rate_limited(sock_net(sk), skb,
|
|
LINUX_MIB_TCPACKSKIPPEDSYNRECV,
|
|
&tcp_rsk(req)->last_oow_ack_time))
|
|
req->rsk_ops->send_ack(sk, skb, req);
|
|
if (paws_reject)
|
|
NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
|
|
return NULL;
|
|
}
|
|
|
|
/* In sequence, PAWS is OK. */
|
|
|
|
/* TODO: We probably should defer ts_recent change once
|
|
* we take ownership of @req.
|
|
*/
|
|
if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_nxt))
|
|
WRITE_ONCE(req->ts_recent, tmp_opt.rcv_tsval);
|
|
|
|
if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
|
|
/* Truncate SYN, it is out of window starting
|
|
at tcp_rsk(req)->rcv_isn + 1. */
|
|
flg &= ~TCP_FLAG_SYN;
|
|
}
|
|
|
|
/* RFC793: "second check the RST bit" and
|
|
* "fourth, check the SYN bit"
|
|
*/
|
|
if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN)) {
|
|
TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
|
|
goto embryonic_reset;
|
|
}
|
|
|
|
/* ACK sequence verified above, just make sure ACK is
|
|
* set. If ACK not set, just silently drop the packet.
|
|
*
|
|
* XXX (TFO) - if we ever allow "data after SYN", the
|
|
* following check needs to be removed.
|
|
*/
|
|
if (!(flg & TCP_FLAG_ACK))
|
|
return NULL;
|
|
|
|
/* For Fast Open no more processing is needed (sk is the
|
|
* child socket).
|
|
*/
|
|
if (fastopen)
|
|
return sk;
|
|
|
|
/* While TCP_DEFER_ACCEPT is active, drop bare ACK. */
|
|
if (req->num_timeout < READ_ONCE(inet_csk(sk)->icsk_accept_queue.rskq_defer_accept) &&
|
|
TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
|
|
inet_rsk(req)->acked = 1;
|
|
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDEFERACCEPTDROP);
|
|
return NULL;
|
|
}
|
|
|
|
/* OK, ACK is valid, create big socket and
|
|
* feed this segment to it. It will repeat all
|
|
* the tests. THIS SEGMENT MUST MOVE SOCKET TO
|
|
* ESTABLISHED STATE. If it will be dropped after
|
|
* socket is created, wait for troubles.
|
|
*/
|
|
child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
|
|
req, &own_req);
|
|
if (!child)
|
|
goto listen_overflow;
|
|
|
|
if (own_req && rsk_drop_req(req)) {
|
|
reqsk_queue_removed(&inet_csk(req->rsk_listener)->icsk_accept_queue, req);
|
|
inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);
|
|
return child;
|
|
}
|
|
|
|
sock_rps_save_rxhash(child, skb);
|
|
tcp_synack_rtt_meas(child, req);
|
|
*req_stolen = !own_req;
|
|
return inet_csk_complete_hashdance(sk, child, req, own_req);
|
|
|
|
listen_overflow:
|
|
if (sk != req->rsk_listener)
|
|
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
|
|
|
|
if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_abort_on_overflow)) {
|
|
inet_rsk(req)->acked = 1;
|
|
return NULL;
|
|
}
|
|
|
|
embryonic_reset:
|
|
if (!(flg & TCP_FLAG_RST)) {
|
|
/* Received a bad SYN pkt - for TFO We try not to reset
|
|
* the local connection unless it's really necessary to
|
|
* avoid becoming vulnerable to outside attack aiming at
|
|
* resetting legit local connections.
|
|
*/
|
|
req->rsk_ops->send_reset(sk, skb);
|
|
} else if (fastopen) { /* received a valid RST pkt */
|
|
reqsk_fastopen_remove(sk, req, true);
|
|
tcp_reset(sk, skb);
|
|
}
|
|
if (!fastopen) {
|
|
bool unlinked = inet_csk_reqsk_queue_drop(sk, req);
|
|
|
|
if (unlinked)
|
|
__NET_INC_STATS(sock_net(sk), LINUX_MIB_EMBRYONICRSTS);
|
|
*req_stolen = !unlinked;
|
|
}
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL(tcp_check_req);
|
|
|
|
/*
|
|
* Queue segment on the new socket if the new socket is active,
|
|
* otherwise we just shortcircuit this and continue with
|
|
* the new socket.
|
|
*
|
|
* For the vast majority of cases child->sk_state will be TCP_SYN_RECV
|
|
* when entering. But other states are possible due to a race condition
|
|
* where after __inet_lookup_established() fails but before the listener
|
|
* locked is obtained, other packets cause the same connection to
|
|
* be created.
|
|
*/
|
|
|
|
enum skb_drop_reason tcp_child_process(struct sock *parent, struct sock *child,
|
|
struct sk_buff *skb)
|
|
__releases(&((child)->sk_lock.slock))
|
|
{
|
|
enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
|
|
int state = child->sk_state;
|
|
|
|
/* record sk_napi_id and sk_rx_queue_mapping of child. */
|
|
sk_mark_napi_id_set(child, skb);
|
|
|
|
tcp_segs_in(tcp_sk(child), skb);
|
|
if (!sock_owned_by_user(child)) {
|
|
reason = tcp_rcv_state_process(child, skb);
|
|
/* Wakeup parent, send SIGIO */
|
|
if (state == TCP_SYN_RECV && child->sk_state != state)
|
|
parent->sk_data_ready(parent);
|
|
} else {
|
|
/* Alas, it is possible again, because we do lookup
|
|
* in main socket hash table and lock on listening
|
|
* socket does not protect us more.
|
|
*/
|
|
__sk_add_backlog(child, skb);
|
|
}
|
|
|
|
bh_unlock_sock(child);
|
|
sock_put(child);
|
|
return reason;
|
|
}
|
|
EXPORT_SYMBOL(tcp_child_process);
|