diff options
author | ps <ps@FreeBSD.org> | 2005-04-10 05:24:59 +0000 |
---|---|---|
committer | ps <ps@FreeBSD.org> | 2005-04-10 05:24:59 +0000 |
commit | ebd6b162f88b784455e9995a341013d78332cbc0 (patch) | |
tree | 663deb5d16b5f5ca6390d4a71eb617e1137dd44f /sys/netinet/tcp_input.c | |
parent | f6d14de55c90b68a7b8c2be07727978a4da1f908 (diff) | |
download | FreeBSD-src-ebd6b162f88b784455e9995a341013d78332cbc0.zip FreeBSD-src-ebd6b162f88b784455e9995a341013d78332cbc0.tar.gz |
- Tighten up the Timestamp checks to prevent a spoofed segment from
setting ts_recent to an arbitrary value, stopping further
communication between the two hosts.
- If the Echoed Timestamp is greater than the current time,
fall back to the non RFC 1323 RTT calculation.
Submitted by: Raja Mukerji (raja at moselle dot com)
Reviewed by: Noritoshi Demizu, Mohan Srinivasan
Diffstat (limited to 'sys/netinet/tcp_input.c')
-rw-r--r-- | sys/netinet/tcp_input.c | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c index 2ed59ce..d89bc2b 100644 --- a/sys/netinet/tcp_input.c +++ b/sys/netinet/tcp_input.c @@ -1701,11 +1701,25 @@ trimthenstep6: /* * If last ACK falls within this segment's sequence numbers, * record its timestamp. - * NOTE that the test is modified according to the latest - * proposal of the tcplw@cray.com list (Braden 1993/04/26). + * NOTE: + * 1) That the test incorporates suggestions from the latest + * proposal of the tcplw@cray.com list (Braden 1993/04/26). + * 2) That updating only on newer timestamps interferes with + * our earlier PAWS tests, so this check should be solely + * predicated on the sequence space of this segment. + * 3) That we modify the segment boundary check to be + * Last.ACK.Sent <= SEG.SEQ + SEG.Len + * instead of RFC1323's + * Last.ACK.Sent < SEG.SEQ + SEG.Len, + * This modified check allows us to overcome RFC1323's + * limitations as described in Stevens TCP/IP Illustrated + * Vol. 2 p.869. In such cases, we can still calculate the + * RTT correctly when RCV.NXT == Last.ACK.Sent. */ if ((to.to_flags & TOF_TS) != 0 && - SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { + SEQ_LEQ(th->th_seq, tp->last_ack_sent) && + SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + + ((thflags & (TH_SYN|TH_FIN)) != 0))) { tp->ts_recent_age = ticks; tp->ts_recent = to.to_tsval; } @@ -2560,6 +2574,12 @@ tcp_dooptions(tp, to, cp, cnt, is_syn, th) bcopy((char *)cp + 6, (char *)&to->to_tsecr, sizeof(to->to_tsecr)); to->to_tsecr = ntohl(to->to_tsecr); + /* + * If echoed timestamp is later than the current time, + * fall back to non RFC1323 RTT calculation. + */ + if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) + to->to_tsecr = 0; break; #ifdef TCP_SIGNATURE /* |