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Fix comments and address ordering in IpAddress::getLocalAddress

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The old code says "The method here is to connect a UDP socket to
anyone (here to localhost)", but connecting to `localhost` doesn't
work because the connection would go via the loopback interface which
always has a local address of `127.0.0.1`.

The current code works on little-endian platforms due to a mistake in
the `createAddress` call. We pass `ntohl(INADDR_LOOPBACK)` as the IP,
but since `INADDR_LOOPBACK` is already in host order this actually
connects to `1.0.0.127`.

Fix the comments and intentionally connect to `1.1.1.1` (as a known
public IP address). This also fixes this call for big-endian
platforms.
This commit is contained in:
James Cowgill 2025-02-16 13:34:58 +00:00 committed by Chris Thrasher
parent f59913e997
commit 91327373b0
1 changed files with 5 additions and 3 deletions
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8
src/SFML/Network/IpAddress.cpp
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@ -124,7 +124,7 @@ std::uint32_t IpAddress::toInteger() const
////////////////////////////////////////////////////////////
std::optional<IpAddress> IpAddress::getLocalAddress()
{
// The method here is to connect a UDP socket to anyone (here to localhost),
// The method here is to connect a UDP socket to a public ip,
// and get the local socket address with the getsockname function.
// UDP connection will not send anything to the network, so this function won't cause any overhead.
@ -136,8 +136,10 @@ std::optional<IpAddress> IpAddress::getLocalAddress()
return std::nullopt;
}
// Connect the socket to localhost on any port
sockaddr_in address = priv::SocketImpl::createAddress(ntohl(INADDR_LOOPBACK), 9);
// Connect the socket to a public ip (here 1.1.1.1) on any
// port. This will give the local address of the network interface
// used for default routing which is usually what we want.
sockaddr_in address = priv::SocketImpl::createAddress(0x01010101, 9);
if (connect(sock, reinterpret_cast<sockaddr*>(&address), sizeof(address)) == -1)
{
priv::SocketImpl::close(sock);