net: diag: Add support to filter on device index

Add support to inet_diag facility to filter sockets based on device
index. If an interface index is in the filter only sockets bound
to that index (sk_bound_dev_if) are returned.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 25af124..38c2c47 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -44,6 +44,7 @@
 	u16 dport;
 	u16 family;
 	u16 userlocks;
+	u32 ifindex;
 };
 
 static DEFINE_MUTEX(inet_diag_table_mutex);
@@ -571,6 +572,14 @@
 			yes = 0;
 			break;
 		}
+		case INET_DIAG_BC_DEV_COND: {
+			u32 ifindex;
+
+			ifindex = *((const u32 *)(op + 1));
+			if (ifindex != entry->ifindex)
+				yes = 0;
+			break;
+		}
 		}
 
 		if (yes) {
@@ -613,6 +622,7 @@
 	entry_fill_addrs(&entry, sk);
 	entry.sport = inet->inet_num;
 	entry.dport = ntohs(inet->inet_dport);
+	entry.ifindex = sk->sk_bound_dev_if;
 	entry.userlocks = sk_fullsock(sk) ? sk->sk_userlocks : 0;
 
 	return inet_diag_bc_run(bc, &entry);
@@ -636,6 +646,17 @@
 	return 0;
 }
 
+/* data is u32 ifindex */
+static bool valid_devcond(const struct inet_diag_bc_op *op, int len,
+			  int *min_len)
+{
+	/* Check ifindex space. */
+	*min_len += sizeof(u32);
+	if (len < *min_len)
+		return false;
+
+	return true;
+}
 /* Validate an inet_diag_hostcond. */
 static bool valid_hostcond(const struct inet_diag_bc_op *op, int len,
 			   int *min_len)
@@ -700,6 +721,10 @@
 			if (!valid_hostcond(bc, len, &min_len))
 				return -EINVAL;
 			break;
+		case INET_DIAG_BC_DEV_COND:
+			if (!valid_devcond(bc, len, &min_len))
+				return -EINVAL;
+			break;
 		case INET_DIAG_BC_S_GE:
 		case INET_DIAG_BC_S_LE:
 		case INET_DIAG_BC_D_GE: