An INIT whose init_tag matches the peer's vtag does not provide new state information. It indicates either: - a stale INIT (after INIT-ACK has already been seen on the same side), or - a retransmitted INIT (after INIT has already been recorded on the same side). In both cases, the INIT must not update ct->proto.sctp.init[] state, since it does not advance the handshake tracking and may otherwise corrupt INIT/INIT-ACK validation logic. Allow INIT processing only when the conntrack entry is newly created (SCTP_CONNTRACK_NONE), or when the init_tag differs from the stored peer vtag. Note it skips the check for the ct with old_state SCTP_CONNTRACK_NONE in nf_conntrack_sctp_packet(), as it is just created in sctp_new() where it set ct->proto.sctp.vtag[IP_CT_DIR_REPLY] = ih->init_tag. Fixes: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.") Signed-off-by: Xin Long --- net/netfilter/nf_conntrack_proto_sctp.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c index 645d2c43ebf7..7e10fa65cbdd 100644 --- a/net/netfilter/nf_conntrack_proto_sctp.c +++ b/net/netfilter/nf_conntrack_proto_sctp.c @@ -466,9 +466,13 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct, if (!ih) goto out_unlock; - if (ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir]) - ct->proto.sctp.init[!dir] = 0; - ct->proto.sctp.init[dir] = 1; + /* Do not record INIT matching peer vtag (stale or retransmitted INIT). */ + if (old_state == SCTP_CONNTRACK_NONE || + ct->proto.sctp.vtag[!dir] != ih->init_tag) { + 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; -- 2.47.1