net: Allow ipv6 proxies and arp proxies be shown with iproute2

Add ability to return neighbour proxies list to caller if
it sent full ndmsg structure and has NTF_PROXY flag set.

Before this patch (and before iproute2 patches):
$ ip neigh add proxy 2001::1 dev eth0
$ ip -6 neigh show
$

After it and with applied iproute2 patches:
$ ip neigh add proxy 2001::1 dev eth0
$ ip -6 neigh show
2001::1 dev eth0  proxy
$

Compatibility with old versions of iproute2 is not broken,
kernel checks for incoming structure size and properly
works if old structure is came.

[v2]
* changed comments style.
* removed useless line with continue and curly bracket.
* changed incoming message size check from equal to more or
  equal.

CC: davem@davemloft.net
CC: kuznet@ms2.inr.ac.ru
CC: netdev@vger.kernel.org
CC: xemul@parallels.com
Signed-off-by: Tony Zelenoff <antonz@parallels.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 87 insertions, 3 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e287346e0934..f98ec444133a 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2165,6 +2165,35 @@ nla_put_failure:
         return -EMSGSIZE;
 }
 
+static int pneigh_fill_info(struct sk_buff *skb, struct pneigh_entry *pn,
+                            u32 pid, u32 seq, int type, unsigned int flags,
+                            struct neigh_table *tbl)
+{
+        struct nlmsghdr *nlh;
+        struct ndmsg *ndm;
+
+        nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ndm), flags);
+        if (nlh == NULL)
+                return -EMSGSIZE;
+
+        ndm = nlmsg_data(nlh);
+        ndm->ndm_family  = tbl->family;
+        ndm->ndm_pad1    = 0;
+        ndm->ndm_pad2    = 0;
+        ndm->ndm_flags   = pn->flags | NTF_PROXY;
+        ndm->ndm_type    = NDA_DST;
+        ndm->ndm_ifindex = pn->dev->ifindex;
+        ndm->ndm_state   = NUD_NONE;
+
+        NLA_PUT(skb, NDA_DST, tbl->key_len, pn->key);
+
+        return nlmsg_end(skb, nlh);
+
+nla_put_failure:
+        nlmsg_cancel(skb, nlh);
+        return -EMSGSIZE;
+}
+
 static void neigh_update_notify(struct neighbour *neigh)
 {
         call_netevent_notifiers(NETEVENT_NEIGH_UPDATE, neigh);
@@ -2214,23 +2243,78 @@ out:
         return rc;
 }
 
+static int pneigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
+                             struct netlink_callback *cb)
+{
+        struct pneigh_entry *n;
+        struct net *net = sock_net(skb->sk);
+        int rc, h, s_h = cb->args[3];
+        int idx, s_idx = idx = cb->args[4];
+
+        read_lock_bh(&tbl->lock);
+
+        for (h = 0; h <= PNEIGH_HASHMASK; h++) {
+                if (h < s_h)
+                        continue;
+                if (h > s_h)
+                        s_idx = 0;
+                for (n = tbl->phash_buckets[h], idx = 0; n; n = n->next) {
+                        if (dev_net(n->dev) != net)
+                                continue;
+                        if (idx < s_idx)
+                                goto next;
+                        if (pneigh_fill_info(skb, n, NETLINK_CB(cb->skb).pid,
+                                            cb->nlh->nlmsg_seq,
+                                            RTM_NEWNEIGH,
+                                            NLM_F_MULTI, tbl) <= 0) {
+                                read_unlock_bh(&tbl->lock);
+                                rc = -1;
+                                goto out;
+                        }
+                next:
+                        idx++;
+                }
+        }
+
+        read_unlock_bh(&tbl->lock);
+        rc = skb->len;
+out:
+        cb->args[3] = h;
+        cb->args[4] = idx;
+        return rc;
+
+}
+
 static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 {
         struct neigh_table *tbl;
         int t, family, s_t;
+        int proxy = 0;
+        int err = 0;
 
         read_lock(&neigh_tbl_lock);
         family = ((struct rtgenmsg *) nlmsg_data(cb->nlh))->rtgen_family;
+
+        /* check for full ndmsg structure presence, family member is
+         * the same for both structures
+         */
+        if (nlmsg_len(cb->nlh) >= sizeof(struct ndmsg) &&
+            ((struct ndmsg *) nlmsg_data(cb->nlh))->ndm_flags == NTF_PROXY)
+                proxy = 1;
+
         s_t = cb->args[0];
 
-        for (tbl = neigh_tables, t = 0; tbl; tbl = tbl->next, t++) {
+        for (tbl = neigh_tables, t = 0; tbl && (err >= 0);
+             tbl = tbl->next, t++) {
                 if (t < s_t || (family && tbl->family != family))
                         continue;
                 if (t > s_t)
                         memset(&cb->args[1], 0, sizeof(cb->args) -
                                                 sizeof(cb->args[0]));
-                if (neigh_dump_table(tbl, skb, cb) < 0)
-                        break;
+                if (proxy)
+                        err = pneigh_dump_table(tbl, skb, cb);
+                else
+                        err = neigh_dump_table(tbl, skb, cb);
         }
         read_unlock(&neigh_tbl_lock);