On Mon, May 16, 2016 at 12:24 PM, Alexander Duyck
<alexander.du...@gmail.com> wrote:
> On Sun, May 15, 2016 at 4:42 PM, Tom Herbert <t...@herbertland.com> wrote:
>> Add encap_hlen and ip_tunnel_encap structure to ip6_tnl. Add functions
>> for getting encap hlen, setting up encap on a tunnel, performing
>> encapsulation operation.
>>
>> Signed-off-by: Tom Herbert <t...@herbertland.com>
>> ---
>> include/net/ip6_tunnel.h | 58 ++++++++++++++++++++++++++++++
>> net/ipv4/ip_tunnel_core.c | 5 +++
>> net/ipv6/ip6_tunnel.c | 89
>> +++++++++++++++++++++++++++++++++++++++++------
>> 3 files changed, 141 insertions(+), 11 deletions(-)
>
> So a bisect is pointing to this patch as causing a regression in IPv6
> GRE throughput from 20 Gb/s to .04 Mb/s
>
> <...>
>
>> diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
>> index e79330f..9f0ea85 100644
>> --- a/net/ipv6/ip6_tunnel.c
>> +++ b/net/ipv6/ip6_tunnel.c
>> @@ -1010,7 +1010,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct
>> net_device *dev, __u8 dsfield,
>> struct dst_entry *dst = NULL, *ndst = NULL;
>> struct net_device *tdev;
>> int mtu;
>> - unsigned int max_headroom = sizeof(struct ipv6hdr);
>> + unsigned int max_headroom = sizeof(struct ipv6hdr) + t->hlen;
>> int err = -1;
>>
>> /* NBMA tunnel */
>> @@ -1063,7 +1063,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct
>> net_device *dev, __u8 dsfield,
>> t->parms.name);
>> goto tx_err_dst_release;
>> }
>> - mtu = dst_mtu(dst) - sizeof(*ipv6h);
>> + mtu = dst_mtu(dst) - sizeof(*ipv6h) - t->hlen;
>> if (encap_limit >= 0) {
>> max_headroom += 8;
>> mtu -= 8;
>
> So I am pretty sure this bit here is causing the regression. Your skb
> already has a GRE header added and it is included in skb->len. In the
> tests just below here you are comparing skb->len to mtu, but you now
> have the GRE header included twice so it is going to fail. Odds are
> this should be t->encap_hlen, and not t->hlen.
>
Good catch! Fixing now...
> - Alex
