net: add fdb generic dump routine

This adds a generic dump routine drivers can call. It
should be sufficient to handle any bridging model that
uses the unicast address list. This should be most SR-IOV
enabled NICs.

v2: return error on nlmsg_put and use -EMSGSIZE instead
    of -ENOMEM this is inline other usages
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -1980,6 +1980,37 @@ void rtmsg_ifinfo(int type, struct net_device *dev, unsigned int change)
 		rtnl_set_sk_err(net, RTNLGRP_LINK, err);
 }
 
+static int nlmsg_populate_fdb_fill(struct sk_buff *skb,
+				   struct net_device *dev,
+				   u8 *addr, u32 pid, u32 seq,
+				   int type, unsigned int flags)
+{
+	struct nlmsghdr *nlh;
+	struct ndmsg *ndm;
+
+	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ndm), NLM_F_MULTI);
+	if (!nlh)
+		return -EMSGSIZE;
+
+	ndm = nlmsg_data(nlh);
+	ndm->ndm_family  = AF_BRIDGE;
+	ndm->ndm_pad1	 = 0;
+	ndm->ndm_pad2    = 0;
+	ndm->ndm_flags	 = flags;
+	ndm->ndm_type	 = 0;
+	ndm->ndm_ifindex = dev->ifindex;
+	ndm->ndm_state   = NUD_PERMANENT;
+
+	if (nla_put(skb, NDA_LLADDR, ETH_ALEN, addr))
+		goto nla_put_failure;
+
+	return nlmsg_end(skb, nlh);
+
+nla_put_failure:
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
+}
+
 static int rtnl_fdb_add(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 {
 	struct net *net = sock_net(skb->sk);
@@ -2101,6 +2132,59 @@ static int rtnl_fdb_del(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	return err;
 }
 
+static int nlmsg_populate_fdb(struct sk_buff *skb,
+			      struct netlink_callback *cb,
+			      struct net_device *dev,
+			      int *idx,
+			      struct netdev_hw_addr_list *list)
+{
+	struct netdev_hw_addr *ha;
+	int err;
+	u32 pid, seq;
+
+	pid = NETLINK_CB(cb->skb).pid;
+	seq = cb->nlh->nlmsg_seq;
+
+	list_for_each_entry(ha, &list->list, list) {
+		if (*idx < cb->args[0])
+			goto skip;
+
+		err = nlmsg_populate_fdb_fill(skb, dev, ha->addr,
+					      pid, seq, 0, NTF_SELF);
+		if (err < 0)
+			return err;
+skip:
+		*idx += 1;
+	}
+	return 0;
+}
+
+/**
+ * ndo_dflt_fdb_dump: default netdevice operation to dump an FDB table.
+ * @nlh: netlink message header
+ * @dev: netdevice
+ *
+ * Default netdevice operation to dump the existing unicast address list.
+ * Returns zero on success.
+ */
+int ndo_dflt_fdb_dump(struct sk_buff *skb,
+		      struct netlink_callback *cb,
+		      struct net_device *dev,
+		      int idx)
+{
+	int err;
+
+	netif_addr_lock_bh(dev);
+	err = nlmsg_populate_fdb(skb, cb, dev, &idx, &dev->uc);
+	if (err)
+		goto out;
+	nlmsg_populate_fdb(skb, cb, dev, &idx, &dev->mc);
+out:
+	netif_addr_unlock_bh(dev);
+	return idx;
+}
+EXPORT_SYMBOL(ndo_dflt_fdb_dump);
+
 static int rtnl_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	int idx = 0;