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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id h1-20020a0cf401000000b0065d0dcc28e3sm633041qvl.73.2023.10.03.10.17.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Oct 2023 10:17:57 -0700 (PDT) From: Xin Long To: network dev , netfilter-devel@vger.kernel.org, linux-sctp@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, Eric Dumazet , Paolo Abeni , Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , Marcelo Ricardo Leitner , Simon Horman Subject: [PATCHv2 nf 1/2] netfilter: handle the connecting collision properly in nf_conntrack_proto_sctp Date: Tue, 3 Oct 2023 13:17:53 -0400 Message-Id: <73f4a01458ecac38616447e66a79fe5ef989400c.1696353375.git.lucien.xin@gmail.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org 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: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.") Signed-off-by: Xin Long --- v2: - use __be32 for vtag variable to make Sparse unhappy, as Simon noticed. - add Fixes tag, as Simon suggested. - replace "ih == NULL" with "!ih", as checkpatch.pl suggested. --- include/linux/netfilter/nf_conntrack_sctp.h | 1 + net/netfilter/nf_conntrack_proto_sctp.c | 43 ++++++++++++++++----- 2 files changed, 34 insertions(+), 10 deletions(-) diff --git a/include/linux/netfilter/nf_conntrack_sctp.h b/include/linux/netfilter/nf_conntrack_sctp.h index 625f491b95de..fb31312825ae 100644 --- a/include/linux/netfilter/nf_conntrack_sctp.h +++ b/include/linux/netfilter/nf_conntrack_sctp.h @@ -9,6 +9,7 @@ struct ip_ct_sctp { enum sctp_conntrack state; __be32 vtag[IP_CT_DIR_MAX]; + u8 init[IP_CT_DIR_MAX]; u8 last_dir; u8 flags; }; diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c index b6bcc8f2f46b..c6bd533983c1 100644 --- a/net/netfilter/nf_conntrack_proto_sctp.c +++ b/net/netfilter/nf_conntrack_proto_sctp.c @@ -112,7 +112,7 @@ static const u8 sctp_conntracks[2][11][SCTP_CONNTRACK_MAX] = { /* shutdown_ack */ {sSA, sCL, sCW, sCE, sES, sSA, sSA, sSA, sSA}, /* error */ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sCL},/* Can't have Stale cookie*/ /* cookie_echo */ {sCL, sCL, sCE, sCE, sES, sSS, sSR, sSA, sCL},/* 5.2.4 - Big TODO */ -/* cookie_ack */ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sCL},/* Can't come in orig dir */ +/* cookie_ack */ {sCL, sCL, sCW, sES, sES, sSS, sSR, sSA, sCL},/* Can't come in orig dir */ /* shutdown_comp*/ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sCL, sCL}, /* heartbeat */ {sHS, sCL, sCW, sCE, sES, sSS, sSR, sSA, sHS}, /* heartbeat_ack*/ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sHS}, @@ -126,7 +126,7 @@ static const u8 sctp_conntracks[2][11][SCTP_CONNTRACK_MAX] = { /* shutdown */ {sIV, sCL, sCW, sCE, sSR, sSS, sSR, sSA, sIV}, /* shutdown_ack */ {sIV, sCL, sCW, sCE, sES, sSA, sSA, sSA, sIV}, /* error */ {sIV, sCL, sCW, sCL, sES, sSS, sSR, sSA, sIV}, -/* cookie_echo */ {sIV, sCL, sCW, sCE, sES, sSS, sSR, sSA, sIV},/* Can't come in reply dir */ +/* cookie_echo */ {sIV, sCL, sCE, sCE, sES, sSS, sSR, sSA, sIV},/* Can't come in reply dir */ /* cookie_ack */ {sIV, sCL, sCW, sES, sES, sSS, sSR, sSA, sIV}, /* shutdown_comp*/ {sIV, sCL, sCW, sCE, sES, sSS, sSR, sCL, sIV}, /* heartbeat */ {sIV, sCL, sCW, sCE, sES, sSS, sSR, sSA, sHS}, @@ -412,6 +412,9 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct, /* (D) vtag must be same as init_vtag as found in INIT_ACK */ if (sh->vtag != ct->proto.sctp.vtag[dir]) goto out_unlock; + } else if (sch->type == SCTP_CID_COOKIE_ACK) { + ct->proto.sctp.init[dir] = 0; + ct->proto.sctp.init[!dir] = 0; } else if (sch->type == SCTP_CID_HEARTBEAT) { if (ct->proto.sctp.vtag[dir] == 0) { pr_debug("Setting %d vtag %x for dir %d\n", sch->type, sh->vtag, dir); @@ -461,16 +464,18 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct, } /* If it is an INIT or an INIT ACK note down the vtag */ - if (sch->type == SCTP_CID_INIT || - sch->type == SCTP_CID_INIT_ACK) { - struct sctp_inithdr _inithdr, *ih; + if (sch->type == SCTP_CID_INIT) { + struct sctp_inithdr _ih, *ih; - ih = skb_header_pointer(skb, offset + sizeof(_sch), - sizeof(_inithdr), &_inithdr); - if (ih == NULL) + ih = skb_header_pointer(skb, offset + sizeof(_sch), sizeof(*ih), &_ih); + if (!ih) goto out_unlock; - pr_debug("Setting vtag %x for dir %d\n", - ih->init_tag, !dir); + + if (ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir]) + ct->proto.sctp.init[!dir] = 0; + ct->proto.sctp.init[dir] = 1; + + pr_debug("Setting vtag %x for dir %d\n", ih->init_tag, !dir); ct->proto.sctp.vtag[!dir] = ih->init_tag; /* don't renew timeout on init retransmit so @@ -481,6 +486,24 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct, old_state == SCTP_CONNTRACK_CLOSED && nf_ct_is_confirmed(ct)) ignore = true; + } else if (sch->type == SCTP_CID_INIT_ACK) { + struct sctp_inithdr _ih, *ih; + __be32 vtag; + + ih = skb_header_pointer(skb, offset + sizeof(_sch), sizeof(*ih), &_ih); + if (!ih) + goto out_unlock; + + vtag = ct->proto.sctp.vtag[!dir]; + if (!ct->proto.sctp.init[!dir] && vtag && vtag != ih->init_tag) + goto out_unlock; + /* collision */ + if (ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir] && + vtag != ih->init_tag) + goto out_unlock; + + pr_debug("Setting vtag %x for dir %d\n", ih->init_tag, !dir); + ct->proto.sctp.vtag[!dir] = ih->init_tag; } ct->proto.sctp.state = new_state;