listener: ipv6only socket bind support

According to RFC3493 and most Linux distributions, default value is to
work in IPv4-mapped mode. If there is a requirement to bind same port
on same ip addresses but different handlers for both IPv4 and IPv6,
it is required to set IPV6_V6ONLY socket option to be sure that the
code works as expected without affected by bindv6only sysctl setting
in system.

See an example working with this patch:
https://gist.github.com/demirten/023008a63cd966e48b0ebcf9af7fc113

Closes: #640 (cherry-pick)

1 files changed, 8 insertions, 0 deletions

diff --git a/evutil.c b/evutil.c
index d93eff5f..5d385bdc 100644
--- a/evutil.c
+++ b/evutil.c
@@ -386,6 +386,14 @@ evutil_make_listen_socket_reuseable_port(evutil_socket_t sock)
 }
 
 int
+evutil_make_listen_socket_ipv6only(evutil_socket_t sock)
+{
+	int one = 1;
+	return setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (void*) &one,
+	    (ev_socklen_t)sizeof(one));
+}
+
+int
 evutil_make_tcp_listen_socket_deferred(evutil_socket_t sock)
 {
 #if defined(EVENT__HAVE_NETINET_TCP_H) && defined(TCP_DEFER_ACCEPT)