moonlight-stream/moonlight-common-c
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Implement workaround for bad synthesized IPv6 addresses when connecting through a v4-only VPN on iOS

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This commit is contained in:
Cameron Gutman 2025-07-14 22:27:54 -05:00
parent ab6e21ff5b
commit 0975a8684f
1 changed files with 65 additions and 26 deletions
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91
src/PlatformSockets.c
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@ -600,10 +600,43 @@ int enableNoDelay(SOCKET s) {
return 0;
}
static bool isPrivateNetworkAddressV4(struct sockaddr_in* address, bool matchCGN)
{
unsigned int addr;
memcpy(&addr, &address->sin_addr, sizeof(addr));
addr = htonl(addr);
// 10.0.0.0/8
if ((addr & 0xFF000000) == 0x0A000000) {
return true;
}
// 172.16.0.0/12
else if ((addr & 0xFFF00000) == 0xAC100000) {
return true;
}
// 192.168.0.0/16
else if ((addr & 0xFFFF0000) == 0xC0A80000) {
return true;
}
// 169.254.0.0/16
else if ((addr & 0xFFFF0000) == 0xA9FE0000) {
return true;
}
// 100.64.0.0/10
else if (matchCGN && (addr & 0xFFFC0000) == 0x64400000) {
return true;
}
else {
return false;
}
}
int resolveHostName(const char* host, int family, int tcpTestPort, struct sockaddr_storage* addr, SOCKADDR_LEN* addrLen)
{
struct addrinfo hints, *res, *currentAddr;
int err;
bool needsFallbackV4 = false;
memset(&hints, 0, sizeof(hints));
hints.ai_family = family;
@ -620,11 +653,32 @@ int resolveHostName(const char* host, int family, int tcpTestPort, struct sockad
return -1;
}
#ifdef AF_INET6
{
struct sockaddr_in sin4;
memset(&sin4, 0, sizeof(sin4));
sin4.sin_family = AF_INET;
// As a workaround for broken 464XLAT on iOS where the CLAT synthesizes IPv6
// addresses for on-link IPv4 destinations on other interfaces, we will try
// again with an IPv4-only resolution if we detect that getaddrinfo() resolved
// a private IPv4 address to a single IPv6 address and that address didn't work.
needsFallbackV4 =
family == AF_UNSPEC &&
res->ai_family == AF_INET6 &&
res->ai_next == NULL &&
inet_pton(AF_INET, host, &sin4.sin_addr) == 1 &&
isPrivateNetworkAddressV4(&sin4, true);
}
#endif
for (currentAddr = res; currentAddr != NULL; currentAddr = currentAddr->ai_next) {
// Use the test port to ensure this address is working if:
// a) We have multiple addresses
// b) The caller asked us to test even with a single address
if (tcpTestPort != 0 && (res->ai_next != NULL || (tcpTestPort & TCP_PORT_FLAG_ALWAYS_TEST))) {
// c) We got an IPv6 address synthesized from an IPv4 address
if (tcpTestPort != 0 && (res->ai_next != NULL || (tcpTestPort & TCP_PORT_FLAG_ALWAYS_TEST) || needsFallbackV4)) {
SOCKET testSocket = connectTcpSocket((struct sockaddr_storage*)currentAddr->ai_addr,
(SOCKADDR_LEN)currentAddr->ai_addrlen,
tcpTestPort & TCP_PORT_MASK,
@ -645,9 +699,16 @@ int resolveHostName(const char* host, int family, int tcpTestPort, struct sockad
return 0;
}
Limelog("No working addresses found for host: %s\n", host);
freeaddrinfo(res);
return -1;
if (needsFallbackV4) {
// Fallback to IPv4-only if we didn't find a working address (see comment above)
return resolveHostName(host, AF_INET, tcpTestPort, addr, addrLen);
}
else {
Limelog("No working addresses found for host: %s\n", host);
return -1;
}
}
#ifdef AF_INET6
@ -666,30 +727,8 @@ bool isInSubnetV6(struct sockaddr_in6* sin6, unsigned char* subnet, int prefixLe
#endif
bool isPrivateNetworkAddress(struct sockaddr_storage* address) {
// We only count IPv4 addresses as possibly private for now
if (address->ss_family == AF_INET) {
unsigned int addr;
memcpy(&addr, &((struct sockaddr_in*)address)->sin_addr, sizeof(addr));
addr = htonl(addr);
// 10.0.0.0/8
if ((addr & 0xFF000000) == 0x0A000000) {
return true;
}
// 172.16.0.0/12
else if ((addr & 0xFFF00000) == 0xAC100000) {
return true;
}
// 192.168.0.0/16
else if ((addr & 0xFFFF0000) == 0xC0A80000) {
return true;
}
// 169.254.0.0/16
else if ((addr & 0xFFFF0000) == 0xA9FE0000) {
return true;
}
return isPrivateNetworkAddressV4((struct sockaddr_in*)address, false);
}
#ifdef AF_INET6
else if (address->ss_family == AF_INET6) {