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tcp: setup timestamp offset when write_seq already set

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Found that when randomized tcp offsets are enabled (by default)
TCP client can still start new connections without them. Later,
if server does active close and re-uses sockets in TIME-WAIT
state, new SYN from client can be rejected on PAWS check inside
tcp_timewait_state_process(), because either tw_ts_recent or
rcv_tsval doesn't really have an offset set.

Here is how to reproduce it with LTP netstress tool:
    netstress -R 1 &
    netstress -H 127.0.0.1 -lr 1000000 -a1

    [...]
    < S  seq 1956977072 win 43690 TS val 295618 ecr 459956970
    > .  ack 1956911535 win 342 TS val 459967184 ecr 1547117608
    < R  seq 1956911535 win 0 length 0
+1. < S  seq 1956977072 win 43690 TS val 296640 ecr 459956970
    > S. seq 657450664 ack 1956977073 win 43690 TS val 459968205 ecr 296640

Fixes: 95a22caee3 ("tcp: randomize tcp timestamp offsets for each connection")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexey Kodanev 2017-02-22 13:23:55 +03:00 committed by David S. Miller
parent ec7cb62d18
commit 00355fa5bb
2 changed files with 20 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
net/ipv4/tcp_ipv4.c
View File

@ -145,6 +145,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
struct flowi4 *fl4;
struct rtable *rt;
int err;
u32 seq;
struct ip_options_rcu *inet_opt;
struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
@ -234,12 +235,15 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
sk_setup_caps(sk, &rt->dst);
rt = NULL;
if (!tp->write_seq && likely(!tp->repair))
tp->write_seq = secure_tcp_sequence_number(inet->inet_saddr,
inet->inet_daddr,
inet->inet_sport,
usin->sin_port,
&tp->tsoffset);
if (likely(!tp->repair)) {
seq = secure_tcp_sequence_number(inet->inet_saddr,
inet->inet_daddr,
inet->inet_sport,
usin->sin_port,
&tp->tsoffset);
if (!tp->write_seq)
tp->write_seq = seq;
}
inet->inet_id = tp->write_seq ^ jiffies;

16
net/ipv6/tcp_ipv6.c
View File

@ -122,6 +122,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
struct flowi6 fl6;
struct dst_entry *dst;
int addr_type;
u32 seq;
int err;
struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
@ -285,12 +286,15 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
sk_set_txhash(sk);
if (!tp->write_seq && likely(!tp->repair))
tp->write_seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
sk->sk_v6_daddr.s6_addr32,
inet->inet_sport,
inet->inet_dport,
&tp->tsoffset);
if (likely(!tp->repair)) {
seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
sk->sk_v6_daddr.s6_addr32,
inet->inet_sport,
inet->inet_dport,
&tp->tsoffset);
if (!tp->write_seq)
tp->write_seq = seq;
}
if (tcp_fastopen_defer_connect(sk, &err))
return err;