Core: added support for TCP keepalive parameters on macOS.HEADmaster

The support first appeared in OS X Mavericks 10.9 and documented since
OS X Yosemite 10.10.

It has a subtle implementation difference from other operating systems
in that the TCP_KEEPALIVE socket option (used in place of TCP_KEEPIDLE)
isn't inherited from a listening socket to an accepted socket.

An apparent reason for this behaviour is that it might be preserved for
the sake of backward compatibility.  The TCP_KEEPALIVE socket option is
not inherited since appearance in OS X Panther 10.3, which long predates
two other TCP_KEEPINTVL and TCP_KEEPCNT socket options.

Thanks to Andy Pan for initial work.

1 files changed, 17 insertions, 0 deletions

diff --git a/src/event/ngx_event_accept.c b/src/event/ngx_event_accept.c
index 27038799d..033d7e021 100644
--- a/src/event/ngx_event_accept.c
+++ b/src/event/ngx_event_accept.c
@@ -203,6 +203,23 @@ ngx_event_accept(ngx_event_t *ev)
             }
         }
 
+#if (NGX_HAVE_KEEPALIVE_TUNABLE && NGX_DARWIN)
+
+        /* Darwin doesn't inherit TCP_KEEPALIVE from a listening socket */
+
+        if (ls->keepidle) {
+            if (setsockopt(s, IPPROTO_TCP, TCP_KEEPALIVE,
+                           (const void *) &ls->keepidle, sizeof(int))
+                == -1)
+            {
+                ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_socket_errno,
+                              "setsockopt(TCP_KEEPALIVE, %d) failed, ignored",
+                              ls->keepidle);
+            }
+        }
+
+#endif
+
         *log = ls->log;
 
         c->recv = ngx_recv;