Re: [PATCH v2] geneve: Fix setting ttl value in collect metadata mode

On Wed, Sep 13, 2017 at 4:15 AM, 严海双 [off-list ref] wrote:

quoted

On 2017年9月13日, at 上午7:43, Pravin Shelar [off-list ref] wrote:

On Tue, Sep 12, 2017 at 12:05 AM, Haishuang Yan
[off-list ref] wrote:

quoted

Similar to vxlan/ipip tunnel, if key->tos is zero in collect metadata
mode, tos should also fallback to ip{4,6}_dst_hoplimit.

Signed-off-by: Haishuang Yan <redacted>

---
Changes since v2:
 * Make the commit message more clearer.
---
drivers/net/geneve.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index f640407..d52a65f 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c

@@ -834,11 +834,10 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
       sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
       if (geneve->collect_md) {
               tos = ip_tunnel_ecn_encap(key->tos, ip_hdr(skb), skb);
-               ttl = key->ttl;
       } else {
               tos = ip_tunnel_ecn_encap(fl4.flowi4_tos, ip_hdr(skb), skb);
-               ttl = key->ttl ? : ip4_dst_hoplimit(&rt->dst);
       }
+       ttl = key->ttl ? : ip4_dst_hoplimit(&rt->dst);
       df = key->tun_flags & TUNNEL_DONT_FRAGMENT ? htons(IP_DF) : 0;

This changes user API of Geneve collect-metadata mode. I do not see
good reason for this. Why user can not set right TTL for the flow?

For example, I test this case with script samples/bpf/test_tunnel_bpf.sh,
and modify samples/bpf/tcbpf2_kern.c with following patch:

But user is suppose to specify the TTL in collect-md mode for Geneve
tunnel. That is the API.