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Date: Fri, 13 Sep 2019 16:47:50 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
netdev@...r.kernel.org
Cc: davem@...emloft.net, edumazet@...gle.com, kraig@...gle.com,
zabele@...cast.net, mark.keaton@...theon.com,
Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net] udp: correct reuseport selection with connected
sockets
On Thu, 2019-09-12 at 21:16 -0400, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@...gle.com>
>
> UDP reuseport groups can hold a mix unconnected and connected sockets.
> Ensure that connections only receive all traffic to their 4-tuple.
>
> Fast reuseport returns on the first reuseport match on the assumption
> that all matches are equal. Only if connections are present, return to
> the previous behavior of scoring all sockets.
>
> Record if connections are present and if so (1) treat such connected
> sockets as an independent match from the group, (2) only return
> 2-tuple matches from reuseport and (3) do not return on the first
> 2-tuple reuseport match to allow for a higher scoring match later.
>
> New field has_conns is set without locks. No other fields in the
> bitmap are modified at runtime and the field is only ever set
> unconditionally, so an RMW cannot miss a change.
>
> Fixes: e32ea7e74727 ("soreuseport: fast reuseport UDP socket selection")
> Link: http://lkml.kernel.org/r/CA+FuTSfRP09aJNYRt04SS6qj22ViiOEWaWmLAwX0psk8-PGNxw@mail.gmail.com
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
>
> ---
>
> I was unable to compile some older kernels, so the Fixes tag is based
> on basic analysis, not bisected to by the regression test.
> ---
> include/net/sock_reuseport.h | 20 +++++++++++++++++++-
> net/core/sock_reuseport.c | 15 +++++++++++++--
> net/ipv4/datagram.c | 2 ++
> net/ipv4/udp.c | 5 +++--
> net/ipv6/datagram.c | 2 ++
> net/ipv6/udp.c | 5 +++--
> 6 files changed, 42 insertions(+), 7 deletions(-)
>
> diff --git a/include/net/sock_reuseport.h b/include/net/sock_reuseport.h
> index d9112de85261..43f4a818d88f 100644
> --- a/include/net/sock_reuseport.h
> +++ b/include/net/sock_reuseport.h
> @@ -21,7 +21,8 @@ struct sock_reuseport {
> unsigned int synq_overflow_ts;
> /* ID stays the same even after the size of socks[] grows. */
> unsigned int reuseport_id;
> - bool bind_inany;
> + unsigned int bind_inany:1;
> + unsigned int has_conns:1;
> struct bpf_prog __rcu *prog; /* optional BPF sock selector */
> struct sock *socks[0]; /* array of sock pointers */
> };
> @@ -37,6 +38,23 @@ extern struct sock *reuseport_select_sock(struct sock *sk,
> extern int reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog);
> extern int reuseport_detach_prog(struct sock *sk);
>
> +static inline bool reuseport_has_conns(struct sock *sk, bool set)
> +{
> + struct sock_reuseport *reuse;
> + bool ret = false;
> +
> + rcu_read_lock();
> + reuse = rcu_dereference(sk->sk_reuseport_cb);
> + if (reuse) {
> + if (set)
> + reuse->has_conns = 1;
> + ret = reuse->has_conns;
> + }
> + rcu_read_unlock();
> +
> + return ret;
> +}
> +
> int reuseport_get_id(struct sock_reuseport *reuse);
>
> #endif /* _SOCK_REUSEPORT_H */
> diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
> index 9408f9264d05..f3ceec93f392 100644
> --- a/net/core/sock_reuseport.c
> +++ b/net/core/sock_reuseport.c
> @@ -295,8 +295,19 @@ struct sock *reuseport_select_sock(struct sock *sk,
>
> select_by_hash:
> /* no bpf or invalid bpf result: fall back to hash usage */
> - if (!sk2)
> - sk2 = reuse->socks[reciprocal_scale(hash, socks)];
> + if (!sk2) {
> + int i, j;
> +
> + i = j = reciprocal_scale(hash, socks);
> + while (reuse->socks[i]->sk_state == TCP_ESTABLISHED) {
> + i++;
> + if (i >= reuse->num_socks)
> + i = 0;
> + if (i == j)
> + goto out;
> + }
> + sk2 = reuse->socks[i];
> + }
> }
>
> out:
> diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c
> index 7bd29e694603..9a0fe0c2fa02 100644
> --- a/net/ipv4/datagram.c
> +++ b/net/ipv4/datagram.c
> @@ -15,6 +15,7 @@
> #include <net/sock.h>
> #include <net/route.h>
> #include <net/tcp_states.h>
> +#include <net/sock_reuseport.h>
>
> int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> {
> @@ -69,6 +70,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
> }
> inet->inet_daddr = fl4->daddr;
> inet->inet_dport = usin->sin_port;
> + reuseport_has_conns(sk, true);
> sk->sk_state = TCP_ESTABLISHED;
> sk_set_txhash(sk);
> inet->inet_id = jiffies;
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index d88821c794fb..16486c8b708b 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -423,12 +423,13 @@ static struct sock *udp4_lib_lookup2(struct net *net,
> score = compute_score(sk, net, saddr, sport,
> daddr, hnum, dif, sdif);
> if (score > badness) {
> - if (sk->sk_reuseport) {
> + if (sk->sk_reuseport &&
> + sk->sk_state != TCP_ESTABLISHED) {
> hash = udp_ehashfn(net, daddr, hnum,
> saddr, sport);
> result = reuseport_select_sock(sk, hash, skb,
> sizeof(struct udphdr));
> - if (result)
> + if (result && !reuseport_has_conns(sk, false))
> return result;
> }
> badness = score;
> diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
> index 9ab897ded4df..96f939248d2f 100644
> --- a/net/ipv6/datagram.c
> +++ b/net/ipv6/datagram.c
> @@ -27,6 +27,7 @@
> #include <net/ip6_route.h>
> #include <net/tcp_states.h>
> #include <net/dsfield.h>
> +#include <net/sock_reuseport.h>
>
> #include <linux/errqueue.h>
> #include <linux/uaccess.h>
> @@ -254,6 +255,7 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
> goto out;
> }
>
> + reuseport_has_conns(sk, true);
> sk->sk_state = TCP_ESTABLISHED;
> sk_set_txhash(sk);
> out:
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 827fe7385078..5995fdc99d3f 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -158,13 +158,14 @@ static struct sock *udp6_lib_lookup2(struct net *net,
> score = compute_score(sk, net, saddr, sport,
> daddr, hnum, dif, sdif);
> if (score > badness) {
> - if (sk->sk_reuseport) {
> + if (sk->sk_reuseport &&
> + sk->sk_state != TCP_ESTABLISHED) {
> hash = udp6_ehashfn(net, daddr, hnum,
> saddr, sport);
>
> result = reuseport_select_sock(sk, hash, skb,
> sizeof(struct udphdr));
> - if (result)
> + if (result && !reuseport_has_conns(sk, false))
> return result;
> }
> result = sk;
The patch LGTM,
Acked-by: Paolo Abeni <pabeni@...hat.com>
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