[tcpip] Allow binding to unspecified privileged ports (below 1024)

Originally-implemented-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/src/net/tcpip.c b/src/net/tcpip.c
index 8e187f7e..721a4e48 100644
--- a/src/net/tcpip.c
+++ b/src/net/tcpip.c
@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include <byteswap.h>
@@ -133,3 +134,46 @@ uint16_t generic_tcpip_continue_chksum ( uint16_t partial,
 uint16_t tcpip_chksum ( const void *data, size_t len ) {
 	return tcpip_continue_chksum ( TCPIP_EMPTY_CSUM, data, len );
 }
+
+/**
+ * Bind to local TCP/IP port
+ *
+ * @v st_local		Local TCP/IP socket address, or NULL
+ * @v available		Function to check port availability
+ * @ret port		Local port number, or negative error
+ */
+int tcpip_bind ( struct sockaddr_tcpip *st_local,
+		 int ( * available ) ( int port ) ) {
+	uint16_t flags = 0;
+	uint16_t try_port = 0;
+	uint16_t min_port;
+	uint16_t max_port;
+	unsigned int offset;
+	unsigned int i;
+
+	/* Extract parameters from local socket address */
+	if ( st_local ) {
+		flags = st_local->st_flags;
+		try_port = ntohs ( st_local->st_port );
+	}
+
+	/* If an explicit port is specified, check its availability */
+	if ( try_port )
+		return available ( try_port );
+
+	/* Otherwise, find an available port in the range [1,1023] or
+	 * [1025,65535] as appropriate.
+	 */
+	min_port = ( ( ( ! flags ) & TCPIP_BIND_PRIVILEGED ) + 1 );
+	max_port = ( ( flags & TCPIP_BIND_PRIVILEGED ) - 1 );
+	offset = random();
+	for ( i = 0 ; i <= max_port ; i++ ) {
+		try_port = ( ( i + offset ) & max_port );
+		if ( try_port < min_port )
+			continue;
+		if ( available ( try_port ) < 0 )
+			continue;
+		return try_port;
+	}
+	return -EADDRINUSE;
+}