add vif using local interface index instead of IP

When routing daemon wants to enable forwarding of multicast traffic it
performs something like:

       struct vifctl vc = {
               .vifc_vifi  = 1,
               .vifc_flags = 0,
               .vifc_threshold = 1,
               .vifc_rate_limit = 0,
               .vifc_lcl_addr = ip, /* <--- ip address of physical
interface, e.g. eth0 */
               .vifc_rmt_addr.s_addr = htonl(INADDR_ANY),
         };
       setsockopt(fd, IPPROTO_IP, MRT_ADD_VIF, &vc, sizeof(vc));

This leads (in the kernel) to calling  vif_add() function call which
search the (physical) device using assigned IP address:
       dev = ip_dev_find(net, vifc->vifc_lcl_addr.s_addr);

The current API (struct vifctl) does not allow to specify an
interface other way than using it's IP, and if there are more than a
single interface with specified IP only the first one will be found.

The attached patch (against 2.6.30.4) allows to specify an interface
by its index, instead of IP address:

       struct vifctl vc = {
               .vifc_vifi  = 1,
               .vifc_flags = VIFF_USE_IFINDEX,   /* NEW */
               .vifc_threshold = 1,
               .vifc_rate_limit = 0,
               .vifc_lcl_ifindex = if_nametoindex("eth0"),   /* NEW */
               .vifc_rmt_addr.s_addr = htonl(INADDR_ANY),
         };
       setsockopt(fd, IPPROTO_IP, MRT_ADD_VIF, &vc, sizeof(vc));

Signed-off-by: Ilia K. <mail4ilia@gmail.com>
=== modified file 'include/linux/mroute.h'
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/mroute.h b/include/linux/mroute.h
index 08bc776..d5f6915 100644 (file)
--- a/include/linux/mroute.h
+++ b/include/linux/mroute.h
@@ -59,13 +59,18 @@ struct vifctl {
        unsigned char vifc_flags;       /* VIFF_ flags */
        unsigned char vifc_threshold;   /* ttl limit */
        unsigned int vifc_rate_limit;   /* Rate limiter values (NI) */
-       struct in_addr vifc_lcl_addr;   /* Our address */
+       union {
+               struct in_addr vifc_lcl_addr;     /* Local interface address */
+               int            vifc_lcl_ifindex;  /* Local interface index   */
+       };
        struct in_addr vifc_rmt_addr;   /* IPIP tunnel addr */
 };
 
-#define VIFF_TUNNEL    0x1     /* IPIP tunnel */
-#define VIFF_SRCRT     0x2     /* NI */
-#define VIFF_REGISTER  0x4     /* register vif */
+#define VIFF_TUNNEL            0x1     /* IPIP tunnel */
+#define VIFF_SRCRT             0x2     /* NI */
+#define VIFF_REGISTER          0x4     /* register vif */
+#define VIFF_USE_IFINDEX       0x8     /* use vifc_lcl_ifindex instead of
+                                          vifc_lcl_addr to find an interface */
 
 /*
  *     Cache manipulation structures for mrouted and PIMd

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 630a56d..c757f0b 100644 (file)
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -469,8 +469,18 @@ static int vif_add(struct net *net, struct vifctl *vifc, int mrtsock)
                        return err;
                }
                break;
+
+       case VIFF_USE_IFINDEX:
        case 0:
-               dev = ip_dev_find(net, vifc->vifc_lcl_addr.s_addr);
+               if (vifc->vifc_flags == VIFF_USE_IFINDEX) {
+                       dev = dev_get_by_index(net, vifc->vifc_lcl_ifindex);
+                       if (dev && dev->ip_ptr == NULL) {
+                               dev_put(dev);
+                               return -EADDRNOTAVAIL;
+                       }
+               } else
+                       dev = ip_dev_find(net, vifc->vifc_lcl_addr.s_addr);
+
                if (!dev)
                        return -EADDRNOTAVAIL;
                err = dev_set_allmulti(dev, 1);