ping: allow user to specify VRF and source IP

Without this, the options for sending a ping in the context of a VRF are
limited.

We can send a ping with a specific source IP address.  For example:

  ping 10.1.1.3 -I 10.1.1.2

We can send a ping in the context of a Linux VRF.  For example:

  ping 10.1.1.3 -I vrf_red

However, when pinging in the context of a VRF, Linux does not always choose
a sensible source IP address – the source IP might not belong to the VRF.
As a result, the ping won’t get a response.  As a result, we want to be able
to specify both a VRF and a source IP address when initiating a ping.  For
example:

  ping 10.1.1.3 -I vrf_red -I 10.1.1.2

Ping reads in the command line parameters fine and sets up the 'source' and
'device' variables, but currently ignores the device if the source IP
address is non-zero.  This commit adds a branch to ping.c that does the
socket bind to the device even in the case where the source IP is non-zero.
This branch is based on the existing case where source IP is zero, but
simplified a bit because we've already got a source IP address to use.

2 files changed, 37 insertions, 3 deletions

diff --git a/doc/ping.xml b/doc/ping.xml
index b5cea9c..f567523 100644
--- a/doc/ping.xml
+++ b/doc/ping.xml
@@ -269,11 +269,15 @@ xml:id="man.ping">
         <listitem>
           <para>
           <emphasis remap="I">interface</emphasis> is either an
-          address, or an interface name. If
+          address, an interface name or a VRF name. If
           <emphasis remap="I">interface</emphasis> is an address, it
           sets source address to specified interface address. If
-          <emphasis remap="I">interface</emphasis> in an interface
+          <emphasis remap="I">interface</emphasis> is an interface
           name, it sets source interface to specified interface.
+          If <emphasis remap="I">interface</emphasis> is a VRF
+          name, each packet is routed using the corresponding
+          routing table; in this case, the <option>-I</option> option
+          can be repeated to specify a source address.
           NOTE: For IPv6, when doing ping to a link-local scope
           address, link specification (by the '%'-notation in
           <emphasis remap="I">destination</emphasis>, or by this
diff --git a/ping.c b/ping.c
index 34653be..3b3fa33 100644
--- a/ping.c
+++ b/ping.c
@@ -663,7 +663,37 @@ int ping4_run(int argc, char **argv, struct addrinfo *ai, socket_st *sock)
 				error(0, 0, _("Warning: source address might be selected on device other than: %s"), device);
 		}
 		close(probe_fd);
-	} while (0);
+
+	} else if (device) {
+		struct sockaddr_in dst = whereto;
+		struct ifreq ifr;
+		int fd = sock->fd;
+		int rc;
+		int errno_save;
+
+		memset(&ifr, 0, sizeof(ifr));
+		strncpy(ifr.ifr_name, device, IFNAMSIZ - 1);
+
+		enable_capability_raw();
+		rc = setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device) + 1);
+		errno_save = errno;
+		disable_capability_raw();
+
+		if (rc == -1) {
+			if (IN_MULTICAST(ntohl(dst.sin_addr.s_addr))) {
+				struct ip_mreqn imr;
+
+				if (ioctl(fd, SIOCGIFINDEX, &ifr) < 0)
+					error(2, 0, "%s: %s", _("unknown interface"), device);
+				memset(&imr, 0, sizeof(imr));
+				imr.imr_ifindex = ifr.ifr_ifindex;
+				if (setsockopt(fd, SOL_IP, IP_MULTICAST_IF,
+					       &imr, sizeof(imr)) == -1)
+					error(2, errno, "IP_MULTICAST_IF");
+			} else
+				error(2, errno_save, "SO_BINDTODEVICE %s", device);
+		}
+	}
 
 	if (whereto.sin_addr.s_addr == 0)
 		whereto.sin_addr.s_addr = source.sin_addr.s_addr;