net: network device name ifalias support

This patch add support for keeping an additional character alias
associated with an network interface. This is useful for maintaining
the SNMP ifAlias value which is a user defined value. Routers use this
to hold information like which circuit or line it is connected to. It
is just an arbitrary text label on the network device.

There are two exposed interfaces with this patch, the value can be
read/written either via netlink or sysfs.

This could be maintained just by the snmp daemon, but it is more
generally useful for other management tools, and the kernel is good
place to act as an agreed upon interface to store it.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 0 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 71edb8b36341..8862498fd4a6 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -586,6 +586,7 @@ static inline size_t if_nlmsg_size(const struct net_device *dev)
 {
         return NLMSG_ALIGN(sizeof(struct ifinfomsg))
                + nla_total_size(IFNAMSIZ) /* IFLA_IFNAME */
+               + nla_total_size(IFALIASZ) /* IFLA_IFALIAS */
                + nla_total_size(IFNAMSIZ) /* IFLA_QDISC */
                + nla_total_size(sizeof(struct rtnl_link_ifmap))
                + nla_total_size(sizeof(struct rtnl_link_stats))
@@ -640,6 +641,9 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
         if (txq->qdisc_sleeping)
                 NLA_PUT_STRING(skb, IFLA_QDISC, txq->qdisc_sleeping->ops->id);
 
+        if (dev->ifalias)
+                NLA_PUT_STRING(skb, IFLA_IFALIAS, dev->ifalias);
+
         if (1) {
                 struct rtnl_link_ifmap map = {
                         .mem_start   = dev->mem_start,
@@ -713,6 +717,7 @@ const struct nla_policy ifla_policy[IFLA_MAX+1] = {
         [IFLA_LINKMODE]         = { .type = NLA_U8 },
         [IFLA_LINKINFO]         = { .type = NLA_NESTED },
         [IFLA_NET_NS_PID]       = { .type = NLA_U32 },
+        [IFLA_IFALIAS]          = { .type = NLA_STRING, .len = IFALIASZ-1 },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
@@ -853,6 +858,14 @@ static int do_setlink(struct net_device *dev, struct ifinfomsg *ifm,
                 modified = 1;
         }
 
+        if (tb[IFLA_IFALIAS]) {
+                err = dev_set_alias(dev, nla_data(tb[IFLA_IFALIAS]),
+                                    nla_len(tb[IFLA_IFALIAS]));
+                if (err < 0)
+                        goto errout;
+                modified = 1;
+        }
+
         if (tb[IFLA_BROADCAST]) {
                 nla_memcpy(dev->broadcast, tb[IFLA_BROADCAST], dev->addr_len);
                 send_addr_notify = 1;