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Use IP_PMTUDISC_DONT to clamp MSS on Windows

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This commit is contained in:
Cameron Gutman
2019-12-01 15:00:21 -08:00
parent e5b6a2b7a9
commit ceab64c46b
1 changed files with 20 additions and 3 deletions
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23
src/PlatformSockets.c
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@@ -220,10 +220,27 @@ SOCKET connectTcpSocket(struct sockaddr_storage* dstaddr, SOCKADDR_LEN addrlen,
// Note: This only changes the max packet size we can *receive* from the host PC.
// We still must split our own sends into smaller chunks with TCP_NODELAY enabled to
// avoid MTU issues on the way out to to the target.
val = dstaddr->ss_family == AF_INET ? TCPv4_MSS : TCPv6_MSS;
if (setsockopt(s, IPPROTO_TCP, TCP_MAXSEG, &val, sizeof(val)) < 0) {
Limelog("setsockopt(TCP_MAXSEG, %d) failed: %d", val, (int)LastSocketError());
#ifdef LC_WINDOWS
// Windows doesn't support setting TCP_MAXSEG but IP_PMTUDISC_DONT forces the MSS to the protocol
// minimum which is what we want here. Linux doesn't do this (disabling PMTUD just avoids setting DF).
if (dstaddr->ss_family == AF_INET) {
val = IP_PMTUDISC_DONT;
if (setsockopt(s, IPPROTO_IP, IP_MTU_DISCOVER, (char*)&val, sizeof(val)) < 0) {
Limelog("setsockopt(IP_MTU_DISCOVER, IP_PMTUDISC_DONT) failed: %d\n", val, (int)LastSocketError());
}
}
else {
val = IP_PMTUDISC_DONT;
if (setsockopt(s, IPPROTO_IPV6, IPV6_MTU_DISCOVER, (char*)&val, sizeof(val)) < 0) {
Limelog("setsockopt(IPV6_MTU_DISCOVER, IP_PMTUDISC_DONT) failed: %d\n", val, (int)LastSocketError());
}
}
#else
val = dstaddr->ss_family == AF_INET ? TCPv4_MSS : TCPv6_MSS;
if (setsockopt(s, IPPROTO_TCP, TCP_MAXSEG, (char*)&val, sizeof(val)) < 0) {
Limelog("setsockopt(TCP_MAXSEG, %d) failed: %d\n", val, (int)LastSocketError());
}
#endif
// Enable non-blocking I/O for connect timeout support
nonBlocking = setSocketNonBlocking(s, 1) == 0;