On Sun, May 15, 2016 at 4:42 PM, Tom Herbert <[email protected]> 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 <[email protected]>
> ---
> 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.
- Alex
