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net: udp: prefer listeners bound to an address 

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 13:15:33 -08:00 committed by David S. Miller
parent 8e2ea53a83
commit 4cdeeee925
1 changed files with 19 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
net/ipv4/udp.c
View File

@ -380,15 +380,12 @@ static int compute_score(struct sock *sk, struct net *net,
ipv6_only_sock(sk))
return -1;
if (sk->sk_rcv_saddr != daddr)
return -1;
score = (sk->sk_family == PF_INET) ? 2 : 1;
inet = inet_sk(sk);
if (inet->inet_rcv_saddr) {
if (inet->inet_rcv_saddr != daddr)
return -1;
score += 4;
}
if (inet->inet_daddr) {
if (inet->inet_daddr != saddr)
return -1;
@ -464,65 +461,30 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
__be16 sport, __be32 daddr, __be16 dport, int dif,
int sdif, struct udp_table *udptable, struct sk_buff *skb)
{
struct sock *sk, *result;
struct sock *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;
bool exact_dif = udp_lib_exact_dif_match(net, skb);
int score, badness;
u32 hash = 0;
if (hslot->count > 10) {
hash2 = ipv4_portaddr_hash(net, daddr, hnum);
hash2 = ipv4_portaddr_hash(net, daddr, hnum);
slot2 = hash2 & udptable->mask;
hslot2 = &udptable->hash2[slot2];
result = udp4_lib_lookup2(net, saddr, sport,
daddr, hnum, dif, sdif,
exact_dif, hslot2, skb);
if (!result) {
hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
slot2 = hash2 & udptable->mask;
hslot2 = &udptable->hash2[slot2];
if (hslot->count < hslot2->count)
goto begin;
result = udp4_lib_lookup2(net, saddr, sport,
daddr, hnum, dif, sdif,
htonl(INADDR_ANY), hnum, dif, sdif,
exact_dif, hslot2, skb);
if (!result) {
unsigned int old_slot2 = slot2;
hash2 = ipv4_portaddr_hash(net, htonl(INADDR_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 = udp4_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 = 0;
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 = udp_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;
}
}
if (unlikely(IS_ERR(result)))
return NULL;
return result;
}
EXPORT_SYMBOL_GPL(__udp4_lib_lookup);