(Cc'ing Michael Kerrisk)

On Wed, Mar 22, 2017 at 10:18 PM, Eric Dumazet [off-list ref] wrote:

quoted

On Thu, 2017-03-23 at 13:22 +1100, Daurnimator wrote:

quoted

On 9 March 2017 at 14:10, Daurnimator [off-list ref] wrote:

quoted

When debugging https://github.com/daurnimator/lua-http/issues/73 which
uses https://github.com/wahern/dns we ran into an issue where modern
linux kernels return EINVAL if you try and re-use a udp socket.
The issue seems to occur if you go from a local destination ip to a
non-local one.

Did anyone get a chance to look into this issue?

I believe man page is not complete.

A disconnect is needed before another connect()

Is it? Making connect() reentrant is reasonable for connection-less
protocol like UDP, but I don't dig POSIX for the details. If so we need
something like below...

--- a/net/ipv4/datagram.c
+++ b/net/ipv4/datagram.c

@@ -40,7 +40,7 @@ int __ip4_datagram_connect(struct sock *sk, struct

sockaddr *uaddr, int addr_len
        sk_dst_reset(sk);

        oif = sk->sk_bound_dev_if;
-       saddr = inet->inet_saddr;
+       saddr = inet->inet_saddr = 0;
        if (ipv4_is_multicast(usin->sin_addr.s_addr)) {
                if (!oif)
                        oif = inet->mc_index;