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Also clamp MSS of TCP over IPv6 packets.

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This commit is contained in:
Guus Sliepen 2010-01-16 19:32:33 +01:00
parent b1945f70fe
commit 95928f7c29
1 changed files with 39 additions and 21 deletions
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56
src/route.c
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@ -93,49 +93,67 @@ static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
return true;
}
void clamp_mss(node_t *source, node_t *via, vpn_packet_t *packet) {
int i;
int len = ((packet->data[46] >> 4) - 5) * 4;
static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
if(!via || via == myself)
return;
/* Find TCP header */
int start = 0;
uint16_t type = packet->data[12] << 8 | packet->data[13];
if(type == ETH_P_IP && packet->data[23] == 6)
start = 14 + (packet->data[14] & 0xf) * 4;
else if(type == ETH_P_IPV6 && packet->data[20] == 6)
start = 14 + 40;
if(!start || packet->len <= start + 20)
return;
/* Use data offset field to calculate length of options field */
int len = ((packet->data[start + 12] >> 4) - 5) * 4;
/* Search for MSS option header */
for(int i = 0; i < len;) {
if(packet->data[54 + i] == 0)
if(packet->data[start + 20 + i] == 0)
break;
if(packet->data[54 + i] == 1) {
if(packet->data[start + 20 + i] == 1) {
i++;
continue;
}
if(i > len - 2 || i > len - packet->data[55 + i])
if(i > len - 2 || i > len - packet->data[start + 21 + i])
break;
if(packet->data[54 + i] != 2) {
if(packet->data[55 + i] < 2)
if(packet->data[start + 20 + i] != 2) {
if(packet->data[start + 21 + i] < 2)
break;
i += packet->data[55 + i];
i += packet->data[start + 21 + i];
continue;
}
if(packet->data[55] != 4)
if(packet->data[start + 21] != 4)
break;
uint16_t oldmss = packet->data[56 + i] << 8 | packet->data[57 + i];
uint16_t newmss = via->mtu - 54;
uint16_t csum = packet->data[50] << 8 | packet->data[51];
/* Found it */
uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
uint16_t newmss = via->mtu - start - 20;
uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
if(oldmss <= newmss)
break;
ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
packet->data[56 + i] = newmss >> 8;
packet->data[57 + i] = newmss & 0xff;
/* Update the MSS value and the checksum */
packet->data[start + 22 + i] = newmss >> 8;
packet->data[start + 23 + i] = newmss & 0xff;
csum ^= 0xffff;
csum -= oldmss;
csum += newmss;
csum ^= 0xffff;
packet->data[50] = csum >> 8;
packet->data[51] = csum & 0xff;
packet->data[start + 16] = csum >> 8;
packet->data[start + 17] = csum & 0xff;
break;
}
}
@ -375,7 +393,6 @@ static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
return;
}
if(via && via != myself && packet->data[23] == 6 && packet->len >= 58 && (packet->data[46] >> 4) > 5)
clamp_mss(source, via, packet);
send_packet(subnet->owner, packet);
@ -516,6 +533,8 @@ static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
return;
}
clamp_mss(source, via, packet);
send_packet(subnet->owner, packet);
}
@ -790,7 +809,6 @@ static void route_mac(node_t *source, vpn_packet_t *packet) {
}
}
if(via && via != myself && (packet->data[12] << 8 | packet->data[13]) == ETH_P_IP && packet->len >= 58 && packet->data[23] == 6 && (packet->data[46] >> 4) > 5)
clamp_mss(source, via, packet);
send_packet(subnet->owner, packet);