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set mss, adjust checksum

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This commit is contained in:
Brendan O'Dea 2005-09-16 05:54:53 +00:00
parent 739356c34c
commit 58617785d5
1 changed files with 17 additions and 7 deletions
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20
l2tpns.c
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@ -4,7 +4,7 @@
// Copyright (c) 2002 FireBrick (Andrews & Arnold Ltd / Watchfront Ltd) - GPL licenced // Copyright (c) 2002 FireBrick (Andrews & Arnold Ltd / Watchfront Ltd) - GPL licenced
// vim: sw=8 ts=8 // vim: sw=8 ts=8
char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.135 2005-09-16 05:35:31 bodea Exp $"; char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.136 2005-09-16 05:54:53 bodea Exp $";
#include <arpa/inet.h> #include <arpa/inet.h>
#include <assert.h> #include <assert.h>
@ -990,6 +990,8 @@ void adjust_tcp_mss(sessionidt s, tunnelidt t, uint8_t *buf, int len, uint8_t *t
uint8_t *mss = 0; uint8_t *mss = 0;
uint8_t *opts; uint8_t *opts;
uint8_t *data; 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 if ((tcp[13] & 0x3f) & ~(TCP_FLAG_SYN|TCP_FLAG_ACK)) // only want SYN and SYN,ACK
return; return;
@ -1017,15 +1019,23 @@ void adjust_tcp_mss(sessionidt s, tunnelidt t, uint8_t *buf, int len, uint8_t *t
} }
if (!mss) return; // not found if (!mss) return; // not found
if (ntohs(*(uint16_t *) mss) <= MSS) return; // mss OK orig = ntohs(*(uint16_t *) mss);
if (orig <= MSS) return; // mss OK
LOG(5, s, t, "TCP: %s:%u -> %s:%u SYN%s, adjusted mss from %u to %u\n", 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 + 12), 0), ntohs(*(uint16_t *) tcp),
fmtaddr(*(in_addr_t *) (buf + 16), 1), ntohs(*(uint16_t *) (tcp + 2)), fmtaddr(*(in_addr_t *) (buf + 16), 1), ntohs(*(uint16_t *) (tcp + 2)),
(tcp[13] & TCP_FLAG_ACK) ? ",ACK" : "", (tcp[13] & TCP_FLAG_ACK) ? ",ACK" : "", orig, MSS);
ntohs(*(uint16_t *) mss), MSS);
// FIXME // set mss
*(int16_t *) mss = 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 // process outgoing (to tunnel) IP