diff options
Diffstat (limited to 'freebsd/sys/netinet/tcp_syncache.c')
| -rw-r--r-- | freebsd/sys/netinet/tcp_syncache.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/freebsd/sys/netinet/tcp_syncache.c b/freebsd/sys/netinet/tcp_syncache.c index a913f5b6..bfbf9f42 100644 --- a/freebsd/sys/netinet/tcp_syncache.c +++ b/freebsd/sys/netinet/tcp_syncache.c @@ -583,15 +583,28 @@ syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m) /* * If the RST bit is set, check the sequence number to see * if this is a valid reset segment. + * * RFC 793 page 37: * In all states except SYN-SENT, all reset (RST) segments * are validated by checking their SEQ-fields. A reset is * valid if its sequence number is in the window. * - * The sequence number in the reset segment is normally an - * echo of our outgoing acknowlegement numbers, but some hosts - * send a reset with the sequence number at the rightmost edge - * of our receive window, and we have to handle this case. + * RFC 793 page 69: + * There are four cases for the acceptability test for an incoming + * segment: + * + * Segment Receive Test + * Length Window + * ------- ------- ------------------------------------------- + * 0 0 SEG.SEQ = RCV.NXT + * 0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND + * >0 0 not acceptable + * >0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND + * or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND + * + * Note that when receiving a SYN segment in the LISTEN state, + * IRS is set to SEG.SEQ and RCV.NXT is set to SEG.SEQ+1, as + * described in RFC 793, page 66. */ if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) && SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) || |