netdev - [PATCH net] ipv4: implement support for NOPREFIXROUTE ifa flag for ipv4 address

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Date:	Tue, 20 Oct 2015 10:28:45 +0200
From:	Paolo Abeni <pabeni@...hat.com>
To:	netdev@...r.kernel.org
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>
Subject: [PATCH net] ipv4: implement support for NOPREFIXROUTE ifa flag for ipv4 address

Currently adding a new ipv4 address always cause the creation of the
related network route, with default metric. When a host has multiple
interfaces on the same network, multiple routes with the same metric
are created.

If the userspace wants to set specific metric on each routes, i.e.
giving better metric to ethernet links in respect to Wi-Fi ones,
the network routes must be deleted and recreated, which is error-prone.

This patch implements the support for IFA_F_NOPREFIXROUTE for ipv4
address. When an address is added with such flag set, no associated
network route is created, no network route is deleted when
said IP is gone and it's up to the user space manage such route.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/ipv4/fib_frontend.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index d7c2bb0..e786873 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -867,9 +867,10 @@ void fib_add_ifaddr(struct in_ifaddr *ifa)
 
 	if (!ipv4_is_zeronet(prefix) && !(ifa->ifa_flags & IFA_F_SECONDARY) &&
 	    (prefix != addr || ifa->ifa_prefixlen < 32)) {
-		fib_magic(RTM_NEWROUTE,
-			  dev->flags & IFF_LOOPBACK ? RTN_LOCAL : RTN_UNICAST,
-			  prefix, ifa->ifa_prefixlen, prim);
+		if (!(ifa->ifa_flags & IFA_F_NOPREFIXROUTE))
+			fib_magic(RTM_NEWROUTE,
+				  dev->flags & IFF_LOOPBACK ? RTN_LOCAL : RTN_UNICAST,
+				  prefix, ifa->ifa_prefixlen, prim);
 
 		/* Add network specific broadcasts, when it takes a sense */
 		if (ifa->ifa_prefixlen < 31) {
@@ -914,9 +915,10 @@ void fib_del_ifaddr(struct in_ifaddr *ifa, struct in_ifaddr *iprim)
 		}
 	} else if (!ipv4_is_zeronet(any) &&
 		   (any != ifa->ifa_local || ifa->ifa_prefixlen < 32)) {
-		fib_magic(RTM_DELROUTE,
-			  dev->flags & IFF_LOOPBACK ? RTN_LOCAL : RTN_UNICAST,
-			  any, ifa->ifa_prefixlen, prim);
+		if (!(ifa->ifa_flags & IFA_F_NOPREFIXROUTE))
+			fib_magic(RTM_DELROUTE,
+				  dev->flags & IFF_LOOPBACK ? RTN_LOCAL : RTN_UNICAST,
+				  any, ifa->ifa_prefixlen, prim);
 		subnet = 1;
 	}
 
-- 
1.8.3.1

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