add socket_deferaccept

CHANGES

@@ -1,6 +1,7 @@
 0.27:
   add fmt_strm
   add iob_addbuf_munmap
+  add socket_deferaccept
 
 0.26:
   fix really pathological case where io_timeouted would never

socket.h

@@ -50,6 +50,17 @@ int socket_mchopcount6(int s,char hops);
 int socket_mcloop4(int s,char hops);
 int socket_mcloop6(int s,char hops);
 
+/* please note that these are platform specific.  Do not expect them to
+ * work.  You might still get an accept() signalled even though there is
+ * no data available.  So far, DATAIN is supported on FreeBSD and Linux,
+ * and HTTPIN is supported on FreeBSD. */
+enum defermode {
+  DATAIN,	// only signal accept() if there is data coming in
+  HTTPIN,	// only signal accept() if a HTTP header has come in
+};
+
+void socket_deferaccept(int s,enum defermode mode);
+
 void socket_tryreservein(int s,int size);
 
 const char* socket_getifname(uint32 _interface);

socket/socket_deferaccept.c

@@ -0,0 +1,19 @@
+#include "socket.h"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <string.h>
+
+void socket_deferaccept(int s,enum defermode mode) {
+#ifdef TCP_DEFER_ACCEPT
+  int one=1;
+  setsockopt(s,IPPROTO_TCP,TCP_DEFER_ACCEPT,&one,sizeof(one));
+#elif defined(SO_ACCEPTFILTER)
+  struct accept_filter_arg afa;
+  memset(&afa,0,sizeof(afa));
+  strcpy(afa.af_name,mode==HTTPIN?"httpreader":"dataready");
+  setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));
+#endif
+}