allow LWS_SOMAXCONN to be defined at configuretime

Default remains at SOMAXCONN, you can force it at configure time
along these lines

./configure CFLAGS="-DLWS_SOMAXCONN=16384"

Signed-off-by: Andy Green <andy.green@linaro.org>

README-test-server

@@ -145,6 +145,20 @@ you can set it here
  - LWS_MAX_ZLIB_CONN_BUFFER  maximum size a compression buffer is allowed to
 grow to before closing the connection.  Default is 64KBytes.
 
+ - LWS_SOMAXCONN  maximum number of pending connect requests the listening
+socket can cope with.  Default is SOMAXCONN.  If you need to use synthetic
+tests that just spam hundreds of connect requests at once without dropping
+any, you can try setting this to MAX_CLIENTS and mess with your box's tcp
+config like this (courtesy Edwin van der Oetelaar)
+
+echo "2048 64512" > /proc/sys/net/ipv4/ip_local_port_range
+echo "1" > /proc/sys/net/ipv4/tcp_tw_recycle
+echo "1" > /proc/sys/net/ipv4/tcp_tw_reuse
+echo "10" > /proc/sys/net/ipv4/tcp_fin_timeout
+echo "65536" > /proc/sys/net/core/somaxconn
+echo "65536" > /proc/sys/net/ipv4/tcp_max_syn_backlog
+echo "262144" > /proc/sys/net/netfilter/nf_conntrack_max
+
 
 Testing server with a browser
 -----------------------------

lib/libwebsockets.c

@@ -3040,7 +3040,7 @@ libwebsocket_create_context(int port, const char *interf,
 		wsi->mode = LWS_CONNMODE_SERVER_LISTENER;
 		insert_wsi(context, wsi);
 
-		listen(sockfd, SOMAXCONN);
+		listen(sockfd, LWS_SOMAXCONN);
 		lwsl_info(" Listening on port %d\n", port);
 
 		/* list in the internal poll array */

lib/private-libwebsockets.h

@@ -160,6 +160,9 @@ extern void _lws_log(int filter, const char *format, ...);
 #ifndef CIPHERS_LIST_STRING
 #define CIPHERS_LIST_STRING "DEFAULT"
 #endif
+#ifndef LWS_SOMAXCONN
+#define LWS_SOMAXCONN SOMAXCONN
+#endif
 
 #define MAX_WEBSOCKET_04_KEY_LEN 128