set REUSEPORT and REUSEADDR on TCP sockets if needed

When binding a TCP socket, if bind() fails with EADDRINUSE,
try again with REUSEPORT/REUSEADDR (or the equivalent options).

diff --git a/lib/isc/netmgr/tcp.c b/lib/isc/netmgr/tcp.c
index e16bd88d86eeefd497e017663999d10d88ce86c5..9d5e493f31c1f5df71e300803c0e454f9d1f7d3a 100644 (file)
--- a/lib/isc/netmgr/tcp.c
+++ b/lib/isc/netmgr/tcp.c
@@ -454,10 +454,38 @@ isc__nm_async_tcplisten(isc__networker_t *worker, isc__netievent_t *ev0) {
                flags = UV_TCP_IPV6ONLY;
        }
 
-       r = uv_tcp_bind(&sock->uv_handle.tcp, &sock->iface->addr.type.sa,
-                       flags);
+       uv_tcp_bind(&sock->uv_handle.tcp, &sock->iface->addr.type.sa, flags);
+       r = uv_fileno(&sock->uv_handle.handle, (uv_os_fd_t *)&fd);
+       if (r != 0) {
+               isc__nm_incstats(sock->mgr, sock->statsindex[STATID_BINDFAIL]);
+               uv_close(&sock->uv_handle.handle, tcp_close_cb);
+               atomic_store(&sock->result, isc__nm_uverr2result(r));
+               atomic_store(&sock->listen_error, true);
+               goto done;
+       }
+
+       /*
+        * uv_tcp_bind() uses a delayed error, initially returning
+        * success even if bind() fails. By calling uv_tcp_getsockname()
+        * here we can find out whether the bind() call was successful.
+        */
+       r = uv_tcp_getsockname(&sock->uv_handle.tcp, (struct sockaddr *)&sname,
+                              &snamelen);
+
+       if (r == UV_EADDRINUSE && isc__nm_socket_reuse(fd) == ISC_R_SUCCESS &&
+           isc__nm_socket_reuse_lb(fd) == ISC_R_SUCCESS)
+       {
+               /*
+                * Retry bind() with REUSEADDR/REUSEPORT if the address
+                * was in use.
+                */
+               uv_tcp_bind(&sock->uv_handle.tcp, &sock->iface->addr.type.sa,
+                           flags);
+               r = uv_tcp_getsockname(&sock->uv_handle.tcp,
+                                      (struct sockaddr *)&sname, &snamelen);
+       }
+
        if (r == UV_EADDRNOTAVAIL &&
-           uv_fileno(&sock->uv_handle.handle, (uv_os_fd_t *)&fd) == 0 &&
            isc__nm_socket_freebind(fd, sa_family) == ISC_R_SUCCESS)
        {
                /*
@@ -466,8 +494,10 @@ isc__nm_async_tcplisten(isc__networker_t *worker, isc__netievent_t *ev0) {
                 * addresses which are reported by the route socket, although
                 * named is not yet able to properly bind to them.
                 */
-               r = uv_tcp_bind(&sock->uv_handle.tcp,
-                               &sock->iface->addr.type.sa, flags);
+               uv_tcp_bind(&sock->uv_handle.tcp, &sock->iface->addr.type.sa,
+                           flags);
+               r = uv_tcp_getsockname(&sock->uv_handle.tcp,
+                                      (struct sockaddr *)&sname, &snamelen);
        }
 
        if (r != 0) {