X-Git-Url: http://git.sameswireless.fr/l2tpns.git/blobdiff_plain/bde7904f922ed78582ef6289c3896978b51ce7cf..3d2da2d77b5cbbf80e5183b26b44ae2a2c826678:/l2tpns.c diff --git a/l2tpns.c b/l2tpns.c index de1aecc..d36fe59 100644 --- a/l2tpns.c +++ b/l2tpns.c @@ -4,7 +4,7 @@ // Copyright (c) 2002 FireBrick (Andrews & Arnold Ltd / Watchfront Ltd) - GPL licenced // vim: sw=8 ts=8 -char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.133 2005-09-16 05:04:29 bodea Exp $"; +char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.137 2005-09-16 06:10:21 bodea Exp $"; #include #include @@ -988,7 +988,10 @@ void adjust_tcp_mss(sessionidt s, tunnelidt t, uint8_t *buf, int len, uint8_t *t { int d = (tcp[12] >> 4) * 4; uint8_t *mss = 0; + uint8_t *opts; uint8_t *data; + uint16_t orig; + uint32_t sum; if ((tcp[13] & 0x3f) & ~(TCP_FLAG_SYN|TCP_FLAG_ACK)) // only want SYN and SYN,ACK return; @@ -996,35 +999,43 @@ void adjust_tcp_mss(sessionidt s, tunnelidt t, uint8_t *buf, int len, uint8_t *t if (tcp + d > buf + len) // short? return; + opts = tcp + 20; data = tcp + d; - tcp += 20; - while (tcp < data) + while (opts < data) { - if (*tcp == 2 && tcp[1] == 4) // mss option (2), length 4 + if (*opts == 2 && opts[1] == 4) // mss option (2), length 4 { - mss = tcp + 2; + mss = opts + 2; if (mss + 2 > data) return; // short? break; } - if (*tcp == 0) return; // end of options - if (*tcp == 1 || !tcp[1]) // no op (one byte), or no length (prevent loop) - tcp++; + if (*opts == 0) return; // end of options + if (*opts == 1 || !opts[1]) // no op (one byte), or no length (prevent loop) + opts++; else - tcp += tcp[1]; // skip over option + opts += opts[1]; // skip over option } if (!mss) return; // not found - if (ntohl(*(uint16_t *) mss) <= MSS) return; // mss OK + orig = ntohs(*(uint16_t *) mss); - LOG(5, s, t, "TCP: %s:%u -> %s:%u SYN%s, adjusted mss from %u to %u\n", - fmtaddr(*(in_addr_t *)(buf + 12), 0), *(uint16_t *)tcp, - fmtaddr(*(in_addr_t *)(buf + 16), 1), *(uint16_t *)(tcp + 2), - (tcp[13] & TCP_FLAG_ACK) ? ",ACK" : "", - ntohl(*(uint16_t *) mss), MSS); + if (orig <= MSS) return; // mss OK - // FIXME + LOG(5, s, t, "TCP: %s:%u -> %s:%u SYN%s: adjusted mss from %u to %u\n", + fmtaddr(*(in_addr_t *) (buf + 12), 0), ntohs(*(uint16_t *) tcp), + fmtaddr(*(in_addr_t *) (buf + 16), 1), ntohs(*(uint16_t *) (tcp + 2)), + (tcp[13] & TCP_FLAG_ACK) ? ",ACK" : "", orig, MSS); + + // set mss + *(int16_t *) mss = htns(MSS); + + // adjust checksum (see rfc1141) + sum = orig + (~MSS & 0xffff); + sum += ntohs(*(uint16_t *) (tcp + 16)); + sum = (sum & 0xffff) + (sum >> 16); + *(uint16_t *) (tcp + 16) = htons(sum); } // process outgoing (to tunnel) IP