3 files changed, 32 insertions, 5 deletions

diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index 6fafb27877a7..7e1e15f934f3 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -29,6 +29,7 @@ struct ipv4_devconf
         int     no_xfrm;
         int     no_policy;
         int     force_igmp_version;
+        int     promote_secondaries;
         void    *sysctl;
 };
 
@@ -71,6 +72,7 @@ struct in_device
 #define IN_DEV_SEC_REDIRECTS(in_dev)    (ipv4_devconf.secure_redirects || (in_dev)->cnf.secure_redirects)
 #define IN_DEV_IDTAG(in_dev)            ((in_dev)->cnf.tag)
 #define IN_DEV_MEDIUM_ID(in_dev)        ((in_dev)->cnf.medium_id)
+#define IN_DEV_PROMOTE_SECONDARIES(in_dev)      (ipv4_devconf.promote_secondaries || (in_dev)->cnf.promote_secondaries)
 
 #define IN_DEV_RX_REDIRECTS(in_dev) \
         ((IN_DEV_FORWARD(in_dev) && \
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 772998147e3e..23032d9d6071 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -399,6 +399,7 @@ enum
         NET_IPV4_CONF_FORCE_IGMP_VERSION=17,
         NET_IPV4_CONF_ARP_ANNOUNCE=18,
         NET_IPV4_CONF_ARP_IGNORE=19,
+        NET_IPV4_CONF_PROMOTE_SECONDARIES=20,
         __NET_IPV4_CONF_MAX
 };
 
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 = {
                 {