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net: tcp: prefer listeners bound to an address

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A relatively common use case is to have several IPs configured
on a host, and have different listeners for each of them. We would
like to add a "catch all" listener on addr_any, to match incoming
connections not served by any of the listeners bound to a specific
address.

However, port-only lookups can match addr_any sockets when sockets
listening on specific addresses are present if so_reuseport flag
is set. This patch eliminates lookups into port-only hashtable,
as lookups by (addr,port) tuple are easily available.

In addition, compute_score() is tweaked to _not_ match
addr_any sockets to specific addresses, as hash collisions
could result in the unwanted behavior described above.

Tested: the patch compiles; full test in the last patch in this
patchset. Existing reuseport_* selftests also pass.

Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Peter Oskolkov 2018-12-12 13:15:35 -08:00 committed by David S. Miller
parent 23b0269e58
commit d9fbc7f643
1 changed files with 8 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
net/ipv4/inet_hashtables.c
View File

@ -234,24 +234,16 @@ static inline int compute_score(struct sock *sk, struct net *net,
const int dif, const int sdif, bool exact_dif)
{
int score = -1;
struct inet_sock *inet = inet_sk(sk);
bool dev_match;
if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&
if (net_eq(sock_net(sk), net) && sk->sk_num == hnum &&
!ipv6_only_sock(sk)) {
__be32 rcv_saddr = inet->inet_rcv_saddr;
score = sk->sk_family == PF_INET ? 2 : 1;
if (rcv_saddr) {
if (rcv_saddr != daddr)
return -1;
score += 4;
}
dev_match = inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if,
dif, sdif);
if (!dev_match)
if (sk->sk_rcv_saddr != daddr)
return -1;
score += 4;
if (!inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif))
return -1;
score = sk->sk_family == PF_INET ? 2 : 1;
if (sk->sk_incoming_cpu == raw_smp_processor_id())
score++;
}
@ -307,26 +299,12 @@ struct sock *__inet_lookup_listener(struct net *net,
const __be32 daddr, const unsigned short hnum,
const int dif, const int sdif)
{
unsigned int hash = inet_lhashfn(net, hnum);
struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
bool exact_dif = inet_exact_dif_match(net, skb);
struct inet_listen_hashbucket *ilb2;
struct sock *sk, *result = NULL;
int score, hiscore = 0;
struct sock *result = NULL;
unsigned int hash2;
u32 phash = 0;
if (ilb->count <= 10 || !hashinfo->lhash2)
goto port_lookup;
/* Too many sk in the ilb bucket (which is hashed by port alone).
* Try lhash2 (which is hashed by port and addr) instead.
*/
hash2 = ipv4_portaddr_hash(net, daddr, hnum);
ilb2 = inet_lhash2_bucket(hashinfo, hash2);
if (ilb2->count > ilb->count)
goto port_lookup;
result = inet_lhash2_lookup(net, ilb2, skb, doff,
saddr, sport, daddr, hnum,
@ -335,34 +313,12 @@ struct sock *__inet_lookup_listener(struct net *net,
goto done;
/* Lookup lhash2 with INADDR_ANY */
hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
ilb2 = inet_lhash2_bucket(hashinfo, hash2);
if (ilb2->count > ilb->count)
goto port_lookup;
result = inet_lhash2_lookup(net, ilb2, skb, doff,
saddr, sport, daddr, hnum,
saddr, sport, htonl(INADDR_ANY), hnum,
dif, sdif);
goto done;
port_lookup:
sk_for_each_rcu(sk, &ilb->head) {
score = compute_score(sk, net, hnum, daddr,
dif, sdif, exact_dif);
if (score > hiscore) {
if (sk->sk_reuseport) {
phash = inet_ehashfn(net, daddr, hnum,
saddr, sport);
result = reuseport_select_sock(sk, phash,
skb, doff);
if (result)
goto done;
}
result = sk;
hiscore = score;
}
}
done:
if (unlikely(IS_ERR(result)))
return NULL;