From: yupeng <yupeng0921@gmail.com>
Date: Thu, 6 Dec 2018 02:56:28 +0000 (-0800)
Subject: net: call sk_dst_reset when set SO_DONTROUTE
X-Git-Tag: v5.4-rc1~1957^2~131
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=0fbe82e628c817e292ff588cd5847fc935e025f2;p=platform%2Fkernel%2Flinux-rpi.git

net: call sk_dst_reset when set SO_DONTROUTE

after set SO_DONTROUTE to 1, the IP layer should not route packets if
the dest IP address is not in link scope. But if the socket has cached
the dst_entry, such packets would be routed until the sk_dst_cache
expires. So we should clean the sk_dst_cache when a user set
SO_DONTROUTE option. Below are server/client python scripts which
could reprodue this issue:

server side code:

==========================================================================
import socket
import struct
import time

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('0.0.0.0', 9000))
s.listen(1)
sock, addr = s.accept()
sock.setsockopt(socket.SOL_SOCKET, socket.SO_DONTROUTE, struct.pack('i', 1))
while True:
    sock.send(b'foo')
    time.sleep(1)
==========================================================================

client side code:
==========================================================================
import socket
import time

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('server_address', 9000))
while True:
    data = s.recv(1024)
    print(data)
==========================================================================

Signed-off-by: yupeng <yupeng0921@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/core/sock.c b/net/core/sock.c
index f5bb897..f00902c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -700,6 +700,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		break;
 	case SO_DONTROUTE:
 		sock_valbool_flag(sk, SOCK_LOCALROUTE, valbool);
+		sk_dst_reset(sk);
 		break;
 	case SO_BROADCAST:
 		sock_valbool_flag(sk, SOCK_BROADCAST, valbool);