1 files changed, 18 insertions, 4 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 233b5ae87583..1063996f8317 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1244,6 +1244,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
         struct nlattr *tb[IFLA_MAX+1];
         u32 ext_filter_mask = 0;
         int err;
+        int hdrlen;
 
         s_h = cb->args[0];
         s_idx = cb->args[1];
@@ -1251,8 +1252,17 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
         rcu_read_lock();
         cb->seq = net->dev_base_seq;
 
-        if (nlmsg_parse(cb->nlh, sizeof(struct ifinfomsg), tb, IFLA_MAX,
-                        ifla_policy) >= 0) {
+        /* A hack to preserve kernel<->userspace interface.
+         * The correct header is ifinfomsg. It is consistent with rtnl_getlink.
+         * However, before Linux v3.9 the code here assumed rtgenmsg and that's
+         * what iproute2 < v3.9.0 used.
+         * We can detect the old iproute2. Even including the IFLA_EXT_MASK
+         * attribute, its netlink message is shorter than struct ifinfomsg.
+         */
+        hdrlen = nlmsg_len(cb->nlh) < sizeof(struct ifinfomsg) ?
+                 sizeof(struct rtgenmsg) : sizeof(struct ifinfomsg);
+
+        if (nlmsg_parse(cb->nlh, hdrlen, tb, IFLA_MAX, ifla_policy) >= 0) {
 
                 if (tb[IFLA_EXT_MASK])
                         ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
@@ -2126,9 +2136,13 @@ static u16 rtnl_calcit(struct sk_buff *skb, struct nlmsghdr *nlh)
         struct nlattr *tb[IFLA_MAX+1];
         u32 ext_filter_mask = 0;
         u16 min_ifinfo_dump_size = 0;
+        int hdrlen;
+
+        /* Same kernel<->userspace interface hack as in rtnl_dump_ifinfo. */
+        hdrlen = nlmsg_len(nlh) < sizeof(struct ifinfomsg) ?
+                 sizeof(struct rtgenmsg) : sizeof(struct ifinfomsg);
 
-        if (nlmsg_parse(nlh, sizeof(struct ifinfomsg), tb, IFLA_MAX,
-                        ifla_policy) >= 0) {
+        if (nlmsg_parse(nlh, hdrlen, tb, IFLA_MAX, ifla_policy) >= 0) {
                 if (tb[IFLA_EXT_MASK])
                         ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
         }