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, 5 insertions, 0 deletions

diff --git a/listener.c b/listener.c
index 2835df17..e803bed1 100644
--- a/listener.c
+++ b/listener.c
@@ -245,6 +245,11 @@ evconnlistener_new_bind(struct event_base *base, evconnlistener_cb cb,
 			goto err;
 	}
 
+	if (flags & LEV_OPT_BIND_IPV6ONLY) {
+		if (evutil_make_listen_socket_ipv6only(fd) < 0)
+			goto err;
+	}
+
 	if (sa) {
 		if (bind(fd, sa, socklen)<0)
 			goto err;