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net: ipv4: Control SKB reprioritization after forwarding

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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>
This commit is contained in:
Petr Machata
2018-08-01 00:36:03 +02:00
committed by David S. Miller
parent 83ba464515
commit 432e05d328
5 changed files with 22 additions and 1 deletions
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1
net/ipv4/af_inet.c
View File

@@ -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;

3
net/ipv4/ip_forward.c
View File

@@ -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,

9
net/ipv4/sysctl_net_ipv4.c
View File

@@ -663,6 +663,15 @@ static struct ctl_table ipv4_net_table[] = {
.mode = 0644,
.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,