Re: [PATCH net-next] net: ipv4: Add ability to have GRE ignore DF bit in IPv4 payloads

On 07.06.2016 22:42, Philip Prindeville wrote:

On 06/07/2016 02:23 PM, Hannes Frederic Sowa wrote:

quoted

On Tue, Jun 7, 2016, at 21:48, Philip Prindeville wrote:

quoted

  static struct rtnl_link_ops ipgre_link_ops __read_mostly = {

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index d8f5e0a..95649eb 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c

@@ -682,7 +682,7 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct

net_device *dev,
      }
        df = tnl_params->frag_off;
-       if (skb->protocol == htons(ETH_P_IP))
+       if (skb->protocol == htons(ETH_P_IP) && !tunnel->ignore_df)
          df |= (inner_iph->frag_off&htons(IP_DF));
        max_headroom = LL_RESERVED_SPACE(rt->dst.dev) + sizeof(struct
iphdr)

Is still enforce that we inherit the ttl from the inner header to the
outer header if we don't set df bit?

Thanks,
Hannes

That's correct.  That happens a few lines above and we don't change that
behavior with this patch.

It should be discouraged to use this feature, but I have to admit that I
already used stripping of DF bit, too.

Acked-by: Hannes Frederic Sowa <redacted>

Thanks,
Hannes