[gPXE-devel] [PATCHv4 03/10] [tcp] Randomize TCP bind port

Guo-Fu Tseng cooldavid at cooldavid.org
Sat Jul 17 21:26:08 EDT 2010


From: Guo-Fu Tseng <cooldavid at cooldavid.org>

To reduce possible TCP port collision.

Referened: Michael Brown <mcb30 at ipxe.org>
Signed-off-by: Guo-Fu Tseng <cooldavid at cooldavid.org>
---
 src/net/tcp.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/net/tcp.c b/src/net/tcp.c
index 20bcf51..d79dc57 100644
--- a/src/net/tcp.c
+++ b/src/net/tcp.c
@@ -176,13 +176,14 @@ tcp_dump_flags ( struct tcp_connection *tcp, unsigned int flags ) {
  */
 static int tcp_bind ( struct tcp_connection *tcp, unsigned int port ) {
 	struct tcp_connection *existing;
-	static uint16_t try_port = 1023;
+	uint16_t try_port;
+	int i;
 
-	/* If no port specified, find the first available port */
+	/* If no port specified, find an available port */
 	if ( ! port ) {
-		while ( try_port ) {
-			try_port++;
-			if ( try_port < 1024 )
+		try_port = ( random() % 64512 ) + 1023;
+		for ( i = 0 ; i < 65536 ; ++i ) {
+			if ( ++try_port < 1024 )
 				continue;
 			if ( tcp_bind ( tcp, htons ( try_port ) ) == 0 )
 				return 0;
-- 
1.7.1



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