1 files changed, 41 insertions, 7 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 0937b34c27ca..e9f3386a528b 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -641,6 +641,32 @@ void arp_xmit(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(arp_xmit);
 
+static bool arp_is_garp(struct net *net, struct net_device *dev,
+                        int *addr_type, __be16 ar_op,
+                        __be32 sip, __be32 tip,
+                        unsigned char *sha, unsigned char *tha)
+{
+        bool is_garp = tip == sip;
+
+        /* Gratuitous ARP _replies_ also require target hwaddr to be
+         * the same as source.
+         */
+        if (is_garp && ar_op == htons(ARPOP_REPLY))
+                is_garp =
+                        /* IPv4 over IEEE 1394 doesn't provide target
+                         * hardware address field in its ARP payload.
+                         */
+                        tha &&
+                        !memcmp(tha, sha, dev->addr_len);
+
+        if (is_garp) {
+                *addr_type = inet_addr_type_dev_table(net, dev, sip);
+                if (*addr_type != RTN_UNICAST)
+                        is_garp = false;
+        }
+        return is_garp;
+}
+
 /*
  *      Process an arp request.
  */
@@ -653,6 +679,7 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
         unsigned char *arp_ptr;
         struct rtable *rt;
         unsigned char *sha;
+        unsigned char *tha = NULL;
         __be32 sip, tip;
         u16 dev_type = dev->type;
         int addr_type;
@@ -724,6 +751,7 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
                 break;
 #endif
         default:
+                tha = arp_ptr;
                 arp_ptr += dev->addr_len;
         }
         memcpy(&tip, arp_ptr, 4);
@@ -835,19 +863,25 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
 
         n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
 
-        if (IN_DEV_ARP_ACCEPT(in_dev)) {
-                unsigned int addr_type = inet_addr_type_dev_table(net, dev, sip);
+        addr_type = -1;
+        if (n || IN_DEV_ARP_ACCEPT(in_dev)) {
+                is_garp = arp_is_garp(net, dev, &addr_type, arp->ar_op,
+                                      sip, tip, sha, tha);
+        }
 
+        if (IN_DEV_ARP_ACCEPT(in_dev)) {
                 /* Unsolicited ARP is not accepted by default.
                    It is possible, that this option should be enabled for some
                    devices (strip is candidate)
                  */
-                is_garp = arp->ar_op == htons(ARPOP_REQUEST) && tip == sip &&
-                          addr_type == RTN_UNICAST;
-
                 if (!n &&
-                    ((arp->ar_op == htons(ARPOP_REPLY)  &&
-                                addr_type == RTN_UNICAST) || is_garp))
+                    (is_garp ||
+                     (arp->ar_op == htons(ARPOP_REPLY) &&
+                      (addr_type == RTN_UNICAST ||
+                       (addr_type < 0 &&
+                        /* postpone calculation to as late as possible */
+                        inet_addr_type_dev_table(net, dev, sip) ==
+                                RTN_UNICAST)))))
                         n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
         }