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netfilter: handle the connecting collision properly in nf_conntrack_proto_sctp
In Scenario A and B below, as the delayed INIT_ACK always changes the peer
vtag, SCTP ct with the incorrect vtag may cause packet loss.
Scenario A: INIT_ACK is delayed until the peer receives its own INIT_ACK
192.168.1.2 > 192.168.1.1: [INIT] [init tag: 1328086772]
192.168.1.1 > 192.168.1.2: [INIT] [init tag: 1414468151]
192.168.1.2 > 192.168.1.1: [INIT ACK] [init tag: 1328086772]
192.168.1.1 > 192.168.1.2: [INIT ACK] [init tag: 1650211246] *
192.168.1.2 > 192.168.1.1: [COOKIE ECHO]
192.168.1.1 > 192.168.1.2: [COOKIE ECHO]
192.168.1.2 > 192.168.1.1: [COOKIE ACK]
Scenario B: INIT_ACK is delayed until the peer completes its own handshake
192.168.1.2 > 192.168.1.1: sctp (1) [INIT] [init tag: 3922216408]
192.168.1.1 > 192.168.1.2: sctp (1) [INIT] [init tag: 144230885]
192.168.1.2 > 192.168.1.1: sctp (1) [INIT ACK] [init tag: 3922216408]
192.168.1.1 > 192.168.1.2: sctp (1) [COOKIE ECHO]
192.168.1.2 > 192.168.1.1: sctp (1) [COOKIE ACK]
192.168.1.1 > 192.168.1.2: sctp (1) [INIT ACK] [init tag: 3914796021] *
This patch fixes it as below:
In SCTP_CID_INIT processing:
- clear ct->proto.sctp.init[!dir] if ct->proto.sctp.init[dir] &&
ct->proto.sctp.init[!dir]. (Scenario E)
- set ct->proto.sctp.init[dir].
In SCTP_CID_INIT_ACK processing:
- drop it if !ct->proto.sctp.init[!dir] && ct->proto.sctp.vtag[!dir] &&
ct->proto.sctp.vtag[!dir] != ih->init_tag. (Scenario B, Scenario C)
- drop it if ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir] &&
ct->proto.sctp.vtag[!dir] != ih->init_tag. (Scenario A)
In SCTP_CID_COOKIE_ACK processing:
- clear ct->proto.sctp.init[dir] and ct->proto.sctp.init[!dir].
(Scenario D)
Also, it's important to allow the ct state to move forward with cookie_echo
and cookie_ack from the opposite dir for the collision scenarios.
There are also other Scenarios where it should allow the packet through,
addressed by the processing above:
Scenario C: new CT is created by INIT_ACK.
Scenario D: start INIT on the existing ESTABLISHED ct.
Scenario E: start INIT after the old collision on the existing ESTABLISHED
ct.
192.168.1.2 > 192.168.1.1: sctp (1) [INIT] [init tag: 3922216408]
192.168.1.1 > 192.168.1.2: sctp (1) [INIT] [init tag: 144230885]
(both side are stopped, then start new connection again in hours)
192.168.1.2 > 192.168.1.1: sctp (1) [INIT] [init tag: 242308742]
Fixes: 9fb9cbb108
("[NETFILTER]: Add nf_conntrack subsystem.")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
parent
af84f9e447
commit
8e56b063c8
@ -9,6 +9,7 @@ struct ip_ct_sctp {
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enum sctp_conntrack state;
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__be32 vtag[IP_CT_DIR_MAX];
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u8 init[IP_CT_DIR_MAX];
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u8 last_dir;
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u8 flags;
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};
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@ -112,7 +112,7 @@ static const u8 sctp_conntracks[2][11][SCTP_CONNTRACK_MAX] = {
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/* shutdown_ack */ {sSA, sCL, sCW, sCE, sES, sSA, sSA, sSA, sSA},
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/* error */ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sCL},/* Can't have Stale cookie*/
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/* cookie_echo */ {sCL, sCL, sCE, sCE, sES, sSS, sSR, sSA, sCL},/* 5.2.4 - Big TODO */
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/* cookie_ack */ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sCL},/* Can't come in orig dir */
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/* cookie_ack */ {sCL, sCL, sCW, sES, sES, sSS, sSR, sSA, sCL},/* Can't come in orig dir */
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/* shutdown_comp*/ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sCL, sCL},
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/* heartbeat */ {sHS, sCL, sCW, sCE, sES, sSS, sSR, sSA, sHS},
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/* heartbeat_ack*/ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sHS},
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@ -126,7 +126,7 @@ static const u8 sctp_conntracks[2][11][SCTP_CONNTRACK_MAX] = {
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/* shutdown */ {sIV, sCL, sCW, sCE, sSR, sSS, sSR, sSA, sIV},
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/* shutdown_ack */ {sIV, sCL, sCW, sCE, sES, sSA, sSA, sSA, sIV},
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/* error */ {sIV, sCL, sCW, sCL, sES, sSS, sSR, sSA, sIV},
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/* cookie_echo */ {sIV, sCL, sCW, sCE, sES, sSS, sSR, sSA, sIV},/* Can't come in reply dir */
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/* cookie_echo */ {sIV, sCL, sCE, sCE, sES, sSS, sSR, sSA, sIV},/* Can't come in reply dir */
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/* cookie_ack */ {sIV, sCL, sCW, sES, sES, sSS, sSR, sSA, sIV},
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/* shutdown_comp*/ {sIV, sCL, sCW, sCE, sES, sSS, sSR, sCL, sIV},
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/* heartbeat */ {sIV, sCL, sCW, sCE, sES, sSS, sSR, sSA, sHS},
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@ -412,6 +412,9 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct,
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/* (D) vtag must be same as init_vtag as found in INIT_ACK */
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if (sh->vtag != ct->proto.sctp.vtag[dir])
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goto out_unlock;
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} else if (sch->type == SCTP_CID_COOKIE_ACK) {
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ct->proto.sctp.init[dir] = 0;
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ct->proto.sctp.init[!dir] = 0;
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} else if (sch->type == SCTP_CID_HEARTBEAT) {
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if (ct->proto.sctp.vtag[dir] == 0) {
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pr_debug("Setting %d vtag %x for dir %d\n", sch->type, sh->vtag, dir);
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@ -461,16 +464,18 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct,
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}
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/* If it is an INIT or an INIT ACK note down the vtag */
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if (sch->type == SCTP_CID_INIT ||
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sch->type == SCTP_CID_INIT_ACK) {
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struct sctp_inithdr _inithdr, *ih;
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if (sch->type == SCTP_CID_INIT) {
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struct sctp_inithdr _ih, *ih;
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ih = skb_header_pointer(skb, offset + sizeof(_sch),
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sizeof(_inithdr), &_inithdr);
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if (ih == NULL)
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ih = skb_header_pointer(skb, offset + sizeof(_sch), sizeof(*ih), &_ih);
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if (!ih)
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goto out_unlock;
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pr_debug("Setting vtag %x for dir %d\n",
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ih->init_tag, !dir);
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if (ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir])
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ct->proto.sctp.init[!dir] = 0;
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ct->proto.sctp.init[dir] = 1;
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pr_debug("Setting vtag %x for dir %d\n", ih->init_tag, !dir);
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ct->proto.sctp.vtag[!dir] = ih->init_tag;
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/* don't renew timeout on init retransmit so
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@ -481,6 +486,24 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct,
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old_state == SCTP_CONNTRACK_CLOSED &&
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nf_ct_is_confirmed(ct))
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ignore = true;
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} else if (sch->type == SCTP_CID_INIT_ACK) {
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struct sctp_inithdr _ih, *ih;
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__be32 vtag;
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ih = skb_header_pointer(skb, offset + sizeof(_sch), sizeof(*ih), &_ih);
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if (!ih)
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goto out_unlock;
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vtag = ct->proto.sctp.vtag[!dir];
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if (!ct->proto.sctp.init[!dir] && vtag && vtag != ih->init_tag)
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goto out_unlock;
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/* collision */
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if (ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir] &&
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vtag != ih->init_tag)
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goto out_unlock;
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pr_debug("Setting vtag %x for dir %d\n", ih->init_tag, !dir);
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ct->proto.sctp.vtag[!dir] = ih->init_tag;
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}
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ct->proto.sctp.state = new_state;
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