[IPV4]: Primary and secondary addresses

Add an option to make secondary IP addresses get promoted
when primary IP addresses are removed from the device.
It defaults to off to preserve existing behavior.

Signed-off-by: Harald Welte <laforge@gnumonks.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 5 deletions

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 3cc96730c4ed..478a30179a52 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -233,11 +233,14 @@ int inet_addr_onlink(struct in_device *in_dev, u32 a, u32 b)
 static void inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
                          int destroy)
 {
+        struct in_ifaddr *promote = NULL;
         struct in_ifaddr *ifa1 = *ifap;
 
         ASSERT_RTNL();
 
-        /* 1. Deleting primary ifaddr forces deletion all secondaries */
+        /* 1. Deleting primary ifaddr forces deletion all secondaries 
+         * unless alias promotion is set
+         **/
 
         if (!(ifa1->ifa_flags & IFA_F_SECONDARY)) {
                 struct in_ifaddr *ifa;
@@ -251,11 +254,16 @@ static void inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
                                 continue;
                         }
 
-                        *ifap1 = ifa->ifa_next;
+                        if (!IN_DEV_PROMOTE_SECONDARIES(in_dev)) {
+                                *ifap1 = ifa->ifa_next;
 
-                        rtmsg_ifa(RTM_DELADDR, ifa);
-                        notifier_call_chain(&inetaddr_chain, NETDEV_DOWN, ifa);
-                        inet_free_ifa(ifa);
+                                rtmsg_ifa(RTM_DELADDR, ifa);
+                                notifier_call_chain(&inetaddr_chain, NETDEV_DOWN, ifa);
+                                inet_free_ifa(ifa);
+                        } else {
+                                promote = ifa;
+                                break;
+                        }
                 }
         }
 
@@ -281,6 +289,13 @@ static void inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
                 if (!in_dev->ifa_list)
                         inetdev_destroy(in_dev);
         }
+
+        if (promote && IN_DEV_PROMOTE_SECONDARIES(in_dev)) {
+                /* not sure if we should send a delete notify first? */
+                promote->ifa_flags &= ~IFA_F_SECONDARY;
+                rtmsg_ifa(RTM_NEWADDR, promote);
+                notifier_call_chain(&inetaddr_chain, NETDEV_UP, promote);
+        }
 }
 
 static int inet_insert_ifa(struct in_ifaddr *ifa)
@@ -1384,6 +1399,15 @@ static struct devinet_sysctl_table {
                         .proc_handler   = &ipv4_doint_and_flush,
                         .strategy       = &ipv4_doint_and_flush_strategy,
                 },
+                {
+                        .ctl_name       = NET_IPV4_CONF_PROMOTE_SECONDARIES,
+                        .procname       = "promote_secondaries",
+                        .data           = &ipv4_devconf.promote_secondaries,
+                        .maxlen         = sizeof(int),
+                        .mode           = 0644,
+                        .proc_handler   = &ipv4_doint_and_flush,
+                        .strategy       = &ipv4_doint_and_flush_strategy,
+                },
         },
         .devinet_dev = {
                 {