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Date: Fri, 24 Apr 2015 10:28:05 -0700
From: Tom Herbert <tom@...bertland.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>,
"David S. Miller" <davem@...emloft.net>,
Jamal Hadi Salim <jhs@...atatu.com>,
Thomas Graf <tgraf@...g.ch>, jesse@...ira.com, kaber@...sh.net,
Tom Herbert <therbert@...gle.com>, edumazet@...gle.com,
alexander.h.duyck@...hat.com,
Hannes Frederic Sowa <hannes@...essinduktion.org>,
ast@...mgrid.com, daniel@...earbox.net,
herbert@...dor.apana.org.au, cwang@...pensource.com,
john.fastabend@...il.com
Subject: Re: [patch net-next v4 RFC 12/15] flow_dissector: introduce support
for ipv6 addressses
Hi Jiri,
Thanks for this work, I think it's a good direction! Some comments below...
On Fri, Apr 24, 2015 at 8:51 AM, Jiri Pirko <jiri@...nulli.us> wrote:
> So far, only hashes made out of ipv6 addresses could be dissected. This
> patch introduces support for dissection of full ipv6 addresses.
>
> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
> ---
> include/net/flow_dissector.h | 13 +++++++++++++
> net/core/flow_dissector.c | 29 +++++++++++++++++++++--------
> 2 files changed, 34 insertions(+), 8 deletions(-)
>
> diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
> index b67ce84..7c9e84c 100644
> --- a/include/net/flow_dissector.h
> +++ b/include/net/flow_dissector.h
> @@ -3,6 +3,7 @@
>
> #include <linux/types.h>
> #include <linux/skbuff.h>
> +#include <linux/in6.h>
>
> /**
> * struct flow_dissector_key_basic:
> @@ -42,11 +43,23 @@ struct flow_dissector_key_ports {
> };
> };
>
> +/**
> + * struct flow_dissector_key_ipv6_addrs:
> + * @src: source ip address
> + * @dst: destination ip address
> + */
> +struct flow_dissector_key_ipv6_addrs {
> + /* (src,dst) must be grouped, in the same way than in IP header */
> + struct in6_addr src;
> + struct in6_addr dst;
> +};
> +
> enum flow_dissector_key_id {
> FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */
> FLOW_DISSECTOR_KEY_IPV4_ADDRS, /* struct flow_dissector_key_addrs */
> FLOW_DISSECTOR_KEY_IPV6_HASH_ADDRS, /* struct flow_dissector_key_addrs */
> FLOW_DISSECTOR_KEY_PORTS, /* struct flow_dissector_key_ports */
> + FLOW_DISSECTOR_KEY_IPV6_ADDRS, /* struct flow_dissector_key_ipv6_addrs */
>
And we'll want to add VLAN ID, (GRE) key-id, IPv6 flow label, maybe a
couple more.
> FLOW_DISSECTOR_KEY_MAX,
> };
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 564288e..95e9a21 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -175,16 +175,29 @@ ipv6:
> ip_proto = iph->nexthdr;
> nhoff += sizeof(struct ipv6hdr);
>
> - if (!skb_flow_dissector_uses_key(flow_dissector,
> - FLOW_DISSECTOR_KEY_IPV6_HASH_ADDRS))
> - break;
> - key_addrs = skb_flow_dissector_target(flow_dissector,
> - FLOW_DISSECTOR_KEY_IPV6_HASH_ADDRS,
> - target_container);
> + if (skb_flow_dissector_uses_key(flow_dissector,
> + FLOW_DISSECTOR_KEY_IPV6_HASH_ADDRS)) {
> + key_addrs = skb_flow_dissector_target(flow_dissector,
> + FLOW_DISSECTOR_KEY_IPV6_HASH_ADDRS,
> + target_container);
>
> - key_addrs->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
> - key_addrs->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
> + key_addrs->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
> + key_addrs->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
> + goto flow_label;
> + }
So this is still folding the IPv6 addresses so that that we can fit
into jhash_3words? Can we address this now and include the full IPv6
address in the hash? I would propose that we extend the flow_keys
structure (which I think you may already be doing) for full IPv6
address, VLAN, flow label, etc., and then produce a hash across that
whole structure. jhash2 can be used on a structure. jhash is actually
a very efficient hash performance wise-- the rest of flow dissection
is likely the dominant cost anyway. We should also minimize calls to
flow_dissector, I would propose it should be called at most once per
packet-- I'll be reposting patches to fix that in the various qdiscs.
> + if (skb_flow_dissector_uses_key(flow_dissector,
> + FLOW_DISSECTOR_KEY_IPV6_ADDRS)) {
> + struct flow_dissector_key_ipv6_addrs *key_ipv6_addrs;
>
> + key_ipv6_addrs = skb_flow_dissector_target(flow_dissector,
> + FLOW_DISSECTOR_KEY_IPV6_ADDRS,
> + target_container);
> +
> + memcpy(key_ipv6_addrs, &iph->saddr, sizeof(*key_ipv6_addrs));
> + goto flow_label;
> + }
> + break;
> +flow_label:
> flow_label = ip6_flowlabel(iph);
> if (flow_label) {
> /* Awesome, IPv6 packet has a flow label so we can
> --
> 1.9.3
>
> --
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