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net: udp6: 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 13:15:34 -08:00 committed by David S. Miller
parent 4cdeeee925
commit 23b0269e58
1 changed files with 21 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
net/ipv6/udp.c
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@ -125,6 +125,9 @@ static int compute_score(struct sock *sk, struct net *net,
sk->sk_family != PF_INET6)
return -1;
if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))
return -1;
score = 0;
inet = inet_sk(sk);
@ -134,12 +137,6 @@ static int compute_score(struct sock *sk, struct net *net,
score++;
}
if (!ipv6_addr_any(&sk->sk_v6_rcv_saddr)) {
if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))
return -1;
score++;
}
if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
if (!ipv6_addr_equal(&sk->sk_v6_daddr, saddr))
return -1;
@ -197,66 +194,32 @@ struct sock *__udp6_lib_lookup(struct net *net,
int dif, int sdif, struct udp_table *udptable,
struct sk_buff *skb)
{
struct sock *sk, *result;
unsigned short hnum = ntohs(dport);
unsigned int hash2, slot2, slot = udp_hashfn(net, hnum, udptable->mask);
struct udp_hslot *hslot2, *hslot = &udptable->hash[slot];
unsigned int hash2, slot2;
struct udp_hslot *hslot2;
struct sock *result;
bool exact_dif = udp6_lib_exact_dif_match(net, skb);
int score, badness;
u32 hash = 0;
if (hslot->count > 10) {
hash2 = ipv6_portaddr_hash(net, daddr, hnum);
hash2 = ipv6_portaddr_hash(net, daddr, hnum);
slot2 = hash2 & udptable->mask;
hslot2 = &udptable->hash2[slot2];
result = udp6_lib_lookup2(net, saddr, sport,
daddr, hnum, dif, sdif, exact_dif,
hslot2, skb);
if (!result) {
hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
slot2 = hash2 & udptable->mask;
hslot2 = &udptable->hash2[slot2];
if (hslot->count < hslot2->count)
goto begin;
result = udp6_lib_lookup2(net, saddr, sport,
daddr, hnum, dif, sdif, exact_dif,
hslot2, skb);
if (!result) {
unsigned int old_slot2 = slot2;
hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
slot2 = hash2 & udptable->mask;
/* avoid searching the same slot again. */
if (unlikely(slot2 == old_slot2))
return result;
hslot2 = &udptable->hash2[slot2];
if (hslot->count < hslot2->count)
goto begin;
result = udp6_lib_lookup2(net, saddr, sport,
daddr, hnum, dif, sdif,
exact_dif, hslot2,
skb);
}
if (unlikely(IS_ERR(result)))
return NULL;
return result;
}
begin:
result = NULL;
badness = -1;
sk_for_each_rcu(sk, &hslot->head) {
score = compute_score(sk, net, saddr, sport, daddr, hnum, dif,
sdif, exact_dif);
if (score > badness) {
if (sk->sk_reuseport) {
hash = udp6_ehashfn(net, daddr, hnum,
saddr, sport);
result = reuseport_select_sock(sk, hash, skb,
sizeof(struct udphdr));
if (unlikely(IS_ERR(result)))
return NULL;
if (result)
return result;
}
result = sk;
badness = score;
}
&in6addr_any, hnum, dif, sdif,
exact_dif, hslot2,
skb);
}
if (unlikely(IS_ERR(result)))
return NULL;
return result;
}
EXPORT_SYMBOL_GPL(__udp6_lib_lookup);