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

[Pravin Shelar]

On Wed, Sep 13, 2017 at 4:15 AM, 严海双  wrote:
>
>
>> On 2017年9月13日, at 上午7:43, Pravin Shelar  wrote:
>>
>> On Tue, Sep 12, 2017 at 12:05 AM, Haishuang Yan
>>  wrote:
>>> 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 
>>>
>>> ---
>>> 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(>dst);
>>>}
>>> +   ttl = key->ttl ? : ip4_dst_hoplimit(>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.

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

[严海双]

> On 2017年9月13日, at 上午7:43, Pravin Shelar  wrote:
> 
> On Tue, Sep 12, 2017 at 12:05 AM, Haishuang Yan
>  wrote:
>> 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 
>> 
>> ---
>> 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(>dst);
>>}
>> +   ttl = key->ttl ? : ip4_dst_hoplimit(>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:

diff --git a/samples/bpf/tcbpf2_kern.c b/samples/bpf/tcbpf2_kern.c
index 370b749..16b09ed 100644
--- a/samples/bpf/tcbpf2_kern.c
+++ b/samples/bpf/tcbpf2_kern.c
@@ -204,7 +204,6 @@ int _geneve_set_tunnel(struct __sk_buff *skb)
key.remote_ipv4 = 0xac100164; /* 172.16.1.100 */
key.tunnel_id = 2;
key.tunnel_tos = 0;
-   key.tunnel_ttl = 64;

__builtin_memset(, 0x0, sizeof(gopt));
gopt.opt_class = 0x102; /* Open Virtual Networking (OVN) */

The user didn’t set key.tunnel_ttl and then key.tunnel_ttl is 0, so tcpdump 
output on veth1 would have ttl value of 0 in ip header:

PING 10.1.1.100 (10.1.1.100) 56(84) bytes of data.
18:59:27.347373 82:81:85:8a:72:62 > 7e:99:fb:3b:15:73, ethertype IPv4 (0x0800), 
length 104: (tos 0x0, id 7386, offset 0, flags [none], proto UDP
(17), length 90)
64 bytes from 10.1.1.100: icmp_seq=1 ttl=64 time=0.083 ms
172.16.1.200.57776 > 172.16.1.100.6081: [no cksum] UDP, length 62

--- 10.1.1.100 ping statistics —

After my patch, tcpdump output on veth1 would have ttl value of 64 in 
ip header:

PING 10.1.1.100 (10.1.1.100) 56(84) bytes of data.
19:12:10.870410 f2:56:13:68:e9:a9 > 8a:1e:93:dc:59:27, ethertype IPv4 (0x0800), 
length 104: (tos 0x0, ttl 64, id 48595, offset 0, flags [none], p
roto UDP (17), length 90)
64 bytes from 10.1.1.100: icmp_seq=1 ttl=64 time=0.091 ms
172.16.1.200.57776 > 172.16.1.100.6081: [no cksum] UDP, length 62

--- 10.1.1.100 ping statistics ---

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

[Pravin Shelar]

On Tue, Sep 12, 2017 at 12:05 AM, Haishuang Yan
 wrote:
> 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 
>
> ---
> 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(>dst);
> }
> +   ttl = key->ttl ? : ip4_dst_hoplimit(>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?