[IPV6] address: Support NLM_F_EXCL when adding addresses

iproute2 doesn't provide the NLM_F_CREATE flag when adding addresses,
it is assumed to be implied. The existing code issues a check on
said flag when the modify operation fails (likely due to ENOENT)
before continueing to create it, this leads to a hard to predict
result, therefore the NLM_F_CREATE check is removed.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 20 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index bb18b9c3a5cb..1e5a296d0a82 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2908,24 +2908,14 @@ inet6_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
         return inet6_addr_del(ifm->ifa_index, pfx, ifm->ifa_prefixlen);
 }
 
-static int
-inet6_addr_modify(int ifindex, struct in6_addr *pfx,
-                  __u32 prefered_lft, __u32 valid_lft)
+static int inet6_addr_modify(struct inet6_ifaddr *ifp, u32 prefered_lft,
+                             u32 valid_lft)
 {
-        struct inet6_ifaddr *ifp = NULL;
-        struct net_device *dev;
         int ifa_flags = 0;
 
-        if ((dev = __dev_get_by_index(ifindex)) == NULL)
-                return -ENODEV;
-
         if (!valid_lft || (prefered_lft > valid_lft))
                 return -EINVAL;
 
-        ifp = ipv6_get_ifaddr(pfx, dev, 1);
-        if (ifp == NULL)
-                return -ENOENT;
-
         if (valid_lft == INFINITY_LIFE_TIME)
                 ifa_flags = IFA_F_PERMANENT;
         else if (valid_lft >= 0x7FFFFFFF/HZ)
@@ -2947,7 +2937,6 @@ inet6_addr_modify(int ifindex, struct in6_addr *pfx,
         spin_unlock_bh(&ifp->lock);
         if (!(ifp->flags&IFA_F_TENTATIVE))
                 ipv6_ifa_notify(0, ifp);
-        in6_ifa_put(ifp);
 
         addrconf_verify(0);
 
@@ -2960,6 +2949,8 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
         struct ifaddrmsg *ifm;
         struct nlattr *tb[IFA_MAX+1];
         struct in6_addr *pfx;
+        struct inet6_ifaddr *ifa;
+        struct net_device *dev;
         u32 valid_lft, preferred_lft;
         int err;
 
@@ -2983,15 +2974,29 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
                 valid_lft = INFINITY_LIFE_TIME;
         }
 
-        if (nlh->nlmsg_flags & NLM_F_REPLACE) {
-                err = inet6_addr_modify(ifm->ifa_index, pfx,
-                                        preferred_lft, valid_lft);
-                if (err == 0 || !(nlh->nlmsg_flags & NLM_F_CREATE))
-                        return err;
+        dev =  __dev_get_by_index(ifm->ifa_index);
+        if (dev == NULL)
+                return -ENODEV;
+
+        ifa = ipv6_get_ifaddr(pfx, dev, 1);
+        if (ifa == NULL) {
+                /*
+                 * It would be best to check for !NLM_F_CREATE here but
+                 * userspace alreay relies on not having to provide this.
+                 */
+                return inet6_addr_add(ifm->ifa_index, pfx, ifm->ifa_prefixlen,
+                                      preferred_lft, valid_lft);
         }
 
-        return inet6_addr_add(ifm->ifa_index, pfx, ifm->ifa_prefixlen,
-                              preferred_lft, valid_lft);
+        if (nlh->nlmsg_flags & NLM_F_EXCL ||
+            !(nlh->nlmsg_flags & NLM_F_REPLACE))
+                err = -EEXIST;
+        else
+                err = inet6_addr_modify(ifa, preferred_lft, valid_lft);
+
+        in6_ifa_put(ifa);
+
+        return err;
 }
 
 static void put_ifaddrmsg(struct nlmsghdr *nlh, u8 prefixlen, u8 flags,