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authorEric Dumazet <edumazet@google.com>2012-07-19 07:34:03 +0000
committerDavid S. Miller <davem@davemloft.net>2012-07-19 10:35:30 -0700
commitbe9f4a44e7d41cee50ddb5f038fc2391cbbb4046 (patch)
tree184e45a62fa0b4d15961427c0e8d5a496f0617a5 /net/ipv4/ip_output.c
parentaee06da6726d4981c51928c2d6d1e2cabeec7a10 (diff)
ipv4: tcp: remove per net tcp_sock
tcp_v4_send_reset() and tcp_v4_send_ack() use a single socket per network namespace. This leads to bad behavior on multiqueue NICS, because many cpus contend for the socket lock and once socket lock is acquired, extra false sharing on various socket fields slow down the operations. To better resist to attacks, we use a percpu socket. Each cpu can run without contention, using appropriate memory (local node) Additional features : 1) We also mirror the queue_mapping of the incoming skb, so that answers use the same queue if possible. 2) Setting SOCK_USE_WRITE_QUEUE socket flag speedup sock_wfree() 3) We now limit the number of in-flight RST/ACK [1] packets per cpu, instead of per namespace, and we honor the sysctl_wmem_default limit dynamically. (Prior to this patch, sysctl_wmem_default value was copied at boot time, so any further change would not affect tcp_sock limit) [1] These packets are only generated when no socket was matched for the incoming packet. Reported-by: Bill Sommerfeld <wsommerfeld@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Tom Herbert <therbert@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_output.c')
-rw-r--r--net/ipv4/ip_output.c50
1 files changed, 32 insertions, 18 deletions
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index cc52679790b..c528f841ca4 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1463,20 +1463,33 @@ static int ip_reply_glue_bits(void *dptr, char *to, int offset,
/*
* Generic function to send a packet as reply to another packet.
- * Used to send TCP resets so far.
+ * Used to send some TCP resets/acks so far.
*
- * Should run single threaded per socket because it uses the sock
- * structure to pass arguments.
+ * Use a fake percpu inet socket to avoid false sharing and contention.
*/
-void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb, __be32 daddr,
+static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = {
+ .sk = {
+ .__sk_common = {
+ .skc_refcnt = ATOMIC_INIT(1),
+ },
+ .sk_wmem_alloc = ATOMIC_INIT(1),
+ .sk_allocation = GFP_ATOMIC,
+ .sk_flags = (1UL << SOCK_USE_WRITE_QUEUE),
+ },
+ .pmtudisc = IP_PMTUDISC_WANT,
+};
+
+void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
__be32 saddr, const struct ip_reply_arg *arg,
unsigned int len)
{
- struct inet_sock *inet = inet_sk(sk);
struct ip_options_data replyopts;
struct ipcm_cookie ipc;
struct flowi4 fl4;
struct rtable *rt = skb_rtable(skb);
+ struct sk_buff *nskb;
+ struct sock *sk;
+ struct inet_sock *inet;
if (ip_options_echo(&replyopts.opt.opt, skb))
return;
@@ -1494,38 +1507,39 @@ void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb, __be32 daddr,
flowi4_init_output(&fl4, arg->bound_dev_if, 0,
RT_TOS(arg->tos),
- RT_SCOPE_UNIVERSE, sk->sk_protocol,
+ RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
ip_reply_arg_flowi_flags(arg),
daddr, saddr,
tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
- rt = ip_route_output_key(sock_net(sk), &fl4);
+ rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
return;
- /* And let IP do all the hard work.
+ inet = &get_cpu_var(unicast_sock);
- This chunk is not reenterable, hence spinlock.
- Note that it uses the fact, that this function is called
- with locally disabled BH and that sk cannot be already spinlocked.
- */
- bh_lock_sock(sk);
inet->tos = arg->tos;
+ sk = &inet->sk;
sk->sk_priority = skb->priority;
sk->sk_protocol = ip_hdr(skb)->protocol;
sk->sk_bound_dev_if = arg->bound_dev_if;
+ sock_net_set(sk, net);
+ __skb_queue_head_init(&sk->sk_write_queue);
+ sk->sk_sndbuf = sysctl_wmem_default;
ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
&ipc, &rt, MSG_DONTWAIT);
- if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
+ nskb = skb_peek(&sk->sk_write_queue);
+ if (nskb) {
if (arg->csumoffset >= 0)
- *((__sum16 *)skb_transport_header(skb) +
- arg->csumoffset) = csum_fold(csum_add(skb->csum,
+ *((__sum16 *)skb_transport_header(nskb) +
+ arg->csumoffset) = csum_fold(csum_add(nskb->csum,
arg->csum));
- skb->ip_summed = CHECKSUM_NONE;
+ nskb->ip_summed = CHECKSUM_NONE;
+ skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
ip_push_pending_frames(sk, &fl4);
}
- bh_unlock_sock(sk);
+ put_cpu_var(unicast_sock);
ip_rt_put(rt);
}