net: ipv4: Control SKB reprioritization after forwarding
After IPv4 packets are forwarded, the priority of the corresponding SKB
is updated according to the TOS field of IPv4 header. This overrides any
prioritization done earlier by e.g. an skbedit action or ingress-qos-map
defined at a vlan device.
Such overriding may not always be desirable. Even if the packet ends up
being routed, which implies this is an L3 network node, an administrator
may wish to preserve whatever prioritization was done earlier on in the
pipeline.
Therefore introduce a sysctl that controls this behavior. Keep the
default value at 1 to maintain backward-compatible behavior.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index ee707b91d..20fda8f 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1801,6 +1801,7 @@ static __net_init int inet_init_net(struct net *net)
* We set them here, in case sysctl is not compiled.
*/
net->ipv4.sysctl_ip_default_ttl = IPDEFTTL;
+ net->ipv4.sysctl_ip_fwd_update_priority = 1;
net->ipv4.sysctl_ip_dynaddr = 0;
net->ipv4.sysctl_ip_early_demux = 1;
net->ipv4.sysctl_udp_early_demux = 1;
diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index b54b948..32662e9 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -143,7 +143,8 @@ int ip_forward(struct sk_buff *skb)
!skb_sec_path(skb))
ip_rt_send_redirect(skb);
- skb->priority = rt_tos2priority(iph->tos);
+ if (net->ipv4.sysctl_ip_fwd_update_priority)
+ skb->priority = rt_tos2priority(iph->tos);
return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD,
net, NULL, skb, skb->dev, rt->dst.dev,
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 5fa335f..e21dda01 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -664,6 +664,15 @@ static struct ctl_table ipv4_net_table[] = {
.proc_handler = proc_dointvec,
},
{
+ .procname = "ip_forward_update_priority",
+ .data = &init_net.ipv4.sysctl_ip_fwd_update_priority,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
+ {
.procname = "ip_nonlocal_bind",
.data = &init_net.ipv4.sysctl_ip_nonlocal_bind,
.maxlen = sizeof(int),