netdev - Re: [PATCH net-next 03/14] gtp: Call common functions to get tunnel routes and add dst

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Date:   Mon, 18 Sep 2017 21:17:51 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     tom@...ntonium.net
Cc:     netdev@...r.kernel.org, pablo@...filter.org, laforge@...monks.org,
        rohit@...ntonium.net
Subject: Re: [PATCH net-next 03/14] gtp: Call common functions to get
 tunnel routes and add dst_cache

From: Tom Herbert <tom@...ntonium.net>
Date: Mon, 18 Sep 2017 17:38:53 -0700

> Call ip_tunnel_get_route and dst_cache to pdp context which should
> improve performance by obviating the need to perform a route lookup
> on every packet.
> 
> Signed-off-by: Tom Herbert <tom@...ntonium.net>

Not caused by your changes, but something to think about:

> -static struct rtable *ip4_route_output_gtp(struct flowi4 *fl4,
> -					   const struct sock *sk,
> -					   __be32 daddr)
> -{
> -	memset(fl4, 0, sizeof(*fl4));
> -	fl4->flowi4_oif		= sk->sk_bound_dev_if;
> -	fl4->daddr		= daddr;
> -	fl4->saddr		= inet_sk(sk)->inet_saddr;
> -	fl4->flowi4_tos		= RT_CONN_FLAGS(sk);
> -	fl4->flowi4_proto	= sk->sk_protocol;
> -
> -	return ip_route_output_key(sock_net(sk), fl4);
> -}

This and the new dst caching code ignores any source address selection
done by ip_route_output_key() or the new tunnel route lookup helpers.

Either source address selection should be respected, or if saddr will
never be modified by a route lookup for some specific reason here,
that should be documented.