net: Disable LRO on devices that are forwarding

Large Receive Offload (LRO) is only appropriate for packets that are
destined for the host, and should be disabled if received packets may be
forwarded.  It can also confuse the GSO on output.

Add dev_disable_lro() function which uses the appropriate ethtool ops to
disable LRO if enabled.

Add calls to dev_disable_lro() in br_add_if() and functions that enable
IPv4 and IPv6 forwarding.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 9be6be3a7ff3..84127d854cfc 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -348,6 +348,8 @@ static struct inet6_dev * ipv6_add_dev(struct net_device *dev)
                 kfree(ndev);
                 return NULL;
         }
+        if (ndev->cnf.forwarding)
+                dev_disable_lro(dev);
         /* We refer to the device */
         dev_hold(dev);
 
@@ -442,6 +444,8 @@ static void dev_forward_change(struct inet6_dev *idev)
         if (!idev)
                 return;
         dev = idev->dev;
+        if (idev->cnf.forwarding)
+                dev_disable_lro(dev);
         if (dev && (dev->flags & IFF_MULTICAST)) {
                 if (idev->cnf.forwarding)
                         ipv6_dev_mc_inc(dev, &in6addr_linklocal_allrouters);
@@ -487,12 +491,14 @@ static void addrconf_fixup_forwarding(struct ctl_table *table, int *p, int old)
         if (p == &net->ipv6.devconf_dflt->forwarding)
                 return;
 
+        rtnl_lock();
         if (p == &net->ipv6.devconf_all->forwarding) {
                 __s32 newf = net->ipv6.devconf_all->forwarding;
                 net->ipv6.devconf_dflt->forwarding = newf;
                 addrconf_forward_change(net, newf);
         } else if ((!*p) ^ (!old))
                 dev_forward_change((struct inet6_dev *)table->extra1);
+        rtnl_unlock();
 
         if (*p)
                 rt6_purge_dflt_routers(net);