ping: do not bind to device when destination IP is on deviceissue-104

Commit f455fee41c077d4b700a473b2f5b3487b8febc1d made ping to bind to device
when a device argument was given.  But that to does not work if destination
IP on device that socket binds to.  See below how to reproduce this issue.

    # ip addr show dev eth0 | grep 'inet '
        inet 192.168.122.100/24 brd 192.168.122.255 scope global eth0
    # ping -I eth0 192.168.122.100
    PING 192.168.122.100 (192.168.122.100) from 192.168.122.100 eth0: 56(84) bytes of data.
    <nothing... loops forever>

Easiest workaround is to cancel bind to device socket option when source and
destination IPs are the same and device option is defined.

Addresses: https://github.com/iputils/iputils/issues/104
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

1 files changed, 6 insertions, 0 deletions

diff --git a/ping.c b/ping.c
index 791a48e..965c854 100644
--- a/ping.c
+++ b/ping.c
@@ -652,6 +652,12 @@ int ping4_run(int argc, char **argv, struct addrinfo *ai, socket_st *sock)
 					    &source.sin_addr, sizeof(source.sin_addr)))
 					break;
 			}
+			if (ifa && !memcmp(&((struct sockaddr_in *)ifa->ifa_addr)->sin_addr,
+			    &dst.sin_addr, sizeof(source.sin_addr))) {
+				enable_capability_raw();
+				setsockopt(sock->fd, SOL_SOCKET, SO_BINDTODEVICE, "", 0);
+				disable_capability_raw();
+			}
 			freeifaddrs(ifa0);
 			if (!ifa)
 				error(0, 0, "Warning: source address might be selected on device other than: %s", device);