libfetch: support TCP_CORK

Unfortunately libfetch operates on raw sockets and is sending
each HTTP request line using separate syscall which causes the
HTTP request to be sent as multiple packets over the wire in most
configurations. This is not good for performance, but can also
cause subtle breakage if there's DPI firewall that does not get
the Host header.

Incidentally, it seems that on BSDs libfetch already sets
TCP_NOPUSH optimize the packetization. This commit adds same
logic for using TCP_CORK if available. When using TCP_CORK
there is no requirement to set TCP_NODELAY as uncorking will
also cause immediate send. Keep TCP_NODELAY in the fallback
codepaths.

Long term, it might make sense to replace or rewrite libfetch
to use application level buffering.

1 files changed, 22 insertions, 23 deletions

diff --git a/libfetch/http.c b/libfetch/http.c
index 5a515cb..08b2361 100644
--- a/libfetch/http.c
+++ b/libfetch/http.c
@@ -107,6 +107,8 @@
 
 #define HTTP_ERROR(xyz) ((xyz) > 400 && (xyz) < 599)
 
+static int val_yes = 1, val_no = 0;
+
 static int http_cmd(conn_t *, const char *, ...) LIBFETCH_PRINTFLIKE(2, 3);
 
 /*****************************************************************************
@@ -294,21 +296,20 @@ static void
 http_closefn(void *v)
 {
 	struct httpio *io = (struct httpio *)v;
+	conn_t *conn = io->conn;
 
 	if (io->keep_alive) {
-		int val;
-
-		val = 0;
-		setsockopt(io->conn->sd, IPPROTO_TCP, TCP_NODELAY, &val,
-			   sizeof(val));
-			  fetch_cache_put(io->conn, fetch_close);
+#if defined(TCP_CORK)
+		setsockopt(conn->sd, IPPROTO_TCP, TCP_CORK, &val_yes, sizeof val_yes);
+#else
+		setsockopt(conn->sd, IPPROTO_TCP, TCP_NODELAY, &val_no, sizeof val_no);
 #if defined(TCP_NOPUSH) && !defined(__APPLE__)
-		val = 1;
-		setsockopt(io->conn->sd, IPPROTO_TCP, TCP_NOPUSH, &val,
-		    sizeof(val));
+		setsockopt(conn->sd, IPPROTO_TCP, TCP_NOPUSH, &val_yes, sizeof val_yes);
 #endif
+#endif
+		fetch_cache_put(conn, fetch_close);
 	} else {
-		fetch_close(io->conn);
+		fetch_close(conn);
 	}
 
 	free(io->buf);
@@ -688,9 +689,6 @@ http_connect(struct url *URL, struct url *purl, const char *flags, int *cached)
 	hdr_t h;
 	const char *p;
 	int af, verbose;
-#if defined(TCP_NOPUSH) && !defined(__APPLE__)
-	int val;
-#endif
 
 	*cached = 0;
 
@@ -752,9 +750,10 @@ http_connect(struct url *URL, struct url *purl, const char *flags, int *cached)
 		goto ouch;
 	}
 
-#if defined(TCP_NOPUSH) && !defined(__APPLE__)
-	val = 1;
-	setsockopt(conn->sd, IPPROTO_TCP, TCP_NOPUSH, &val, sizeof(val));
+#if defined(TCP_CORK)
+	setsockopt(conn->sd, IPPROTO_TCP, TCP_CORK, &val_yes, sizeof val_yes);
+#elif defined(TCP_NOPUSH) && !defined(__APPLE__)
+	setsockopt(conn->sd, IPPROTO_TCP, TCP_NOPUSH, &val_yes, sizeof val_yes);
 #endif
 
 	return (conn);
@@ -838,7 +837,7 @@ http_request(struct url *URL, const char *op, struct url_stat *us,
 	struct url *url, *new;
 	int chunked, direct, if_modified_since, need_auth, noredirect, nocache;
 	int keep_alive, verbose, cached;
-	int e, i, n, val;
+	int e, i, n;
 	off_t offset, clength, length, size;
 	time_t mtime;
 	const char *p;
@@ -972,14 +971,14 @@ http_request(struct url *URL, const char *op, struct url_stat *us,
 		 * be compatible with such configurations, fiddle with socket
 		 * options to force the pending data to be written.
 		 */
+#if defined(TCP_CORK)
+		setsockopt(conn->sd, IPPROTO_TCP, TCP_CORK, &val_no, sizeof val_no);
+#else
 #if defined(TCP_NOPUSH) && !defined(__APPLE__)
-		val = 0;
-		setsockopt(conn->sd, IPPROTO_TCP, TCP_NOPUSH, &val,
-			   sizeof(val));
+		setsockopt(conn->sd, IPPROTO_TCP, TCP_NOPUSH, &val_no, sizeof val_no);
+#endif
+		setsockopt(conn->sd, IPPROTO_TCP, TCP_NODELAY, &val_yes, sizeof val_yes);
 #endif
-		val = 1;
-		setsockopt(conn->sd, IPPROTO_TCP, TCP_NODELAY, &val,
-			   sizeof(val));
 
 		/* get reply */
 		switch (http_get_reply(conn)) {