From: Nathan Stratton Treadway Date: Sat, 12 Sep 2015 14:33:52 +0000 (+0200) Subject: Fix invalid checksum generation. X-Git-Tag: release-1.1pre12~97 X-Git-Url: https://git.tinc-vpn.org/git/browse?a=commitdiff_plain;h=ae89a25695411149a7499189c9771762ad1f1726;p=tinc Fix invalid checksum generation. Use equation 3 given in RFC 1624 and the UpdateTTL() example function given RFC 1141. # Conflicts: # src/route.c --- diff --git a/src/route.c b/src/route.c index 27851469..70c5806b 100644 --- a/src/route.c +++ b/src/route.c @@ -164,7 +164,7 @@ static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *pac /* Found it */ uint16_t oldmss = DATA(packet)[start + 22 + i] << 8 | DATA(packet)[start + 23 + i]; uint16_t newmss = mtu - start - 20; - uint16_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17]; + uint32_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17]; if(oldmss <= newmss) break; @@ -175,11 +175,13 @@ static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *pac DATA(packet)[start + 22 + i] = newmss >> 8; DATA(packet)[start + 23 + i] = newmss & 0xff; csum ^= 0xffff; - csum -= oldmss; + csum += oldmss ^ 0xffff; csum += newmss; + csum = (csum & 0xffff) + (csum >> 16); + csum += csum >> 16; csum ^= 0xffff; DATA(packet)[start + 16] = csum >> 8; - DATA(packet)[start + 17] = csum & 0xff; + DATA(packet)[start + 17] = csum; break; } }