net: Loopback ifindex is constant now

As pointed out, there are places, that access net->loopback_dev->ifindex
and after ifindex generation is made per-net this value becomes constant
equals 1. So go ahead and introduce the LOOPBACK_IFINDEX constant and use
it where appropriate.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 18 insertions, 10 deletions

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index e2a06fd996d5..4a075babe193 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -197,6 +197,7 @@ static __net_init int loopback_net_init(struct net *net)
         if (err)
                 goto out_free_netdev;
 
+        BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
         net->loopback_dev = dev;
         return 0;
 
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 6dc3db3466bf..97e441945c13 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -105,6 +105,13 @@ struct net {
         struct sock             *diag_nlsk;
 };
 
+/*
+ * ifindex generation is per-net namespace, and loopback is
+ * always the 1st device in ns (see net_dev_init), thus any
+ * loopback device should get ifindex 1
+ */
+
+#define LOOPBACK_IFINDEX        1
 
 #include <linux/seq_file_net.h>
 
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index 85a3604c87c8..c855e8d0738f 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -961,7 +961,7 @@ static int dn_route_output_slow(struct dst_entry **pprt, const struct flowidn *o
                 .saddr = oldflp->saddr,
                 .flowidn_scope = RT_SCOPE_UNIVERSE,
                 .flowidn_mark = oldflp->flowidn_mark,
-                .flowidn_iif = init_net.loopback_dev->ifindex,
+                .flowidn_iif = LOOPBACK_IFINDEX,
                 .flowidn_oif = oldflp->flowidn_oif,
         };
         struct dn_route *rt = NULL;
@@ -979,7 +979,7 @@ static int dn_route_output_slow(struct dst_entry **pprt, const struct flowidn *o
                        "dn_route_output_slow: dst=%04x src=%04x mark=%d"
                        " iif=%d oif=%d\n", le16_to_cpu(oldflp->daddr),
                        le16_to_cpu(oldflp->saddr),
-                       oldflp->flowidn_mark, init_net.loopback_dev->ifindex,
+                       oldflp->flowidn_mark, LOOPBACK_IFINDEX,
                        oldflp->flowidn_oif);
 
         /* If we have an output interface, verify its a DECnet device */
@@ -1042,7 +1042,7 @@ source_ok:
                         if (!fld.daddr)
                                 goto out;
                 }
-                fld.flowidn_oif = init_net.loopback_dev->ifindex;
+                fld.flowidn_oif = LOOPBACK_IFINDEX;
                 res.type = RTN_LOCAL;
                 goto make_route;
         }
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index c43ae3fba792..7f073a38c87d 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -218,7 +218,7 @@ __be32 fib_compute_spec_dst(struct sk_buff *skb)
         scope = RT_SCOPE_UNIVERSE;
         if (!ipv4_is_zeronet(ip_hdr(skb)->saddr)) {
                 fl4.flowi4_oif = 0;
-                fl4.flowi4_iif = net->loopback_dev->ifindex;
+                fl4.flowi4_iif = LOOPBACK_IFINDEX;
                 fl4.daddr = ip_hdr(skb)->saddr;
                 fl4.saddr = 0;
                 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 8eec8f4a0536..3a57570c8ee5 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1798,7 +1798,7 @@ static struct mr_table *ipmr_rt_fib_lookup(struct net *net, struct sk_buff *skb)
                 .flowi4_oif = (rt_is_output_route(rt) ?
                                skb->dev->ifindex : 0),
                 .flowi4_iif = (rt_is_output_route(rt) ?
-                               net->loopback_dev->ifindex :
+                               LOOPBACK_IFINDEX :
                                skb->dev->ifindex),
                 .flowi4_mark = skb->mark,
         };
diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c
index 31371be8174b..c30130062cd6 100644
--- a/net/ipv4/netfilter/ipt_rpfilter.c
+++ b/net/ipv4/netfilter/ipt_rpfilter.c
@@ -85,7 +85,7 @@ static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
                         return ipv4_is_local_multicast(iph->daddr) ^ invert;
                 flow.flowi4_iif = 0;
         } else {
-                flow.flowi4_iif = dev_net(par->in)->loopback_dev->ifindex;
+                flow.flowi4_iif = LOOPBACK_IFINDEX;
         }
 
         flow.daddr = iph->saddr;
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 21ad369014c0..c58137391a3d 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1619,7 +1619,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 
         if (res.type == RTN_LOCAL) {
                 err = fib_validate_source(skb, saddr, daddr, tos,
-                                          net->loopback_dev->ifindex,
+                                          LOOPBACK_IFINDEX,
                                           dev, in_dev, &itag);
                 if (err < 0)
                         goto martian_source_keep_err;
@@ -1895,7 +1895,7 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
 
         orig_oif = fl4->flowi4_oif;
 
-        fl4->flowi4_iif = net->loopback_dev->ifindex;
+        fl4->flowi4_iif = LOOPBACK_IFINDEX;
         fl4->flowi4_tos = tos & IPTOS_RT_MASK;
         fl4->flowi4_scope = ((tos & RTO_ONLINK) ?
                          RT_SCOPE_LINK : RT_SCOPE_UNIVERSE);
@@ -1984,7 +1984,7 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
                 if (!fl4->daddr)
                         fl4->daddr = fl4->saddr = htonl(INADDR_LOOPBACK);
                 dev_out = net->loopback_dev;
-                fl4->flowi4_oif = net->loopback_dev->ifindex;
+                fl4->flowi4_oif = LOOPBACK_IFINDEX;
                 res.type = RTN_LOCAL;
                 flags |= RTCF_LOCAL;
                 goto make_route;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 8e80fd279100..0ddf2d132e7f 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -965,7 +965,7 @@ struct dst_entry * ip6_route_output(struct net *net, const struct sock *sk,
 {
         int flags = 0;
 
-        fl6->flowi6_iif = net->loopback_dev->ifindex;
+        fl6->flowi6_iif = LOOPBACK_IFINDEX;
 
         if ((sk && sk->sk_bound_dev_if) || rt6_need_strict(&fl6->daddr))
                 flags |= RT6_LOOKUP_F_IFACE;