Re: multicast routing and multiple interfaces with same IP

["Ilia K." <mail4ilia@gmail.com>]

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Hi,
I'm attaching a new patch. The changes:
mroute.h:
- consistent name for interface index: vifc_lcl_ifindex
- union of vifc_lcl_addr and vifc_lcl_ifindex since either one of them
can be used
ipmr.c:
- case VIFF_USE_IFINDEX and case 0 had almost the same code, so using
fall through and if to eliminate code duplication

Regards,
Ilia.

On Sat, Aug 29, 2009 at 10:01 AM, David Miller<davem@davemloft.net> wrote:
> From: Octavian Purdila <opurdila@ixiacom.com>
> Date: Thu, 27 Aug 2009 02:53:18 +0300
>
>> I don't have context on multicast routing, but this caught my attention:
>>
>>>@@ -61,11 +61,13 @@
>>>      unsigned int vifc_rate_limit;   /* Rate limiter values (NI) */
>>>      struct in_addr vifc_lcl_addr;   /* Our address */
>>>      struct in_addr vifc_rmt_addr;   /* IPIP tunnel addr */
>>>+     int ifindex;                    /* Local interface index */
>>> };
>>>
>>
>> Wouldn't this break userspace ABI?
>>
>> Perhaps you could use a union between vifc_lcl_addr and vifc_ifindex, they seem
>> to be exclusive.
>
> Indeed, this will need to be fixed up.
>

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=== modified file 'include/linux/mroute.h'
--- include/linux/mroute.h	2009-08-10 11:17:32 +0000
+++ include/linux/mroute.h	2009-09-07 15:16:43 +0000
@@ -59,13 +59,17 @@
 	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 to find an interface */
 
 /*
  *	Cache manipulation structures for mrouted and PIMd

=== modified file 'net/ipv4/ipmr.c'
--- net/ipv4/ipmr.c	2009-08-10 11:17:32 +0000
+++ net/ipv4/ipmr.c	2009-09-07 15:20:07 +0000
@@ -470,8 +470,18 @@
 			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);