[PATCH 3.18 14/20] ipv4: tcp: get rid of ugly unicast_sock

Greg Kroah-Hartman
2015-02-25T02:17:13Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit bdbbb8527b6f6a358dbcb70dac247034d665b8e4 ]

In commit be9f4a44e7d41 ("ipv4: tcp: remove per net tcp_sock")
I tried to address contention on a socket lock, but the solution
I chose was horrible :

commit 3a7c384ffd57e ("ipv4: tcp: unicast_sock should not land outside
of TCP stack") addressed a selinux regression.

commit 0980e56e506b ("ipv4: tcp: set unicast_sock uc_ttl to -1")
took care of another regression.

commit b5ec8eeac46 ("ipv4: fix ip_send_skb()") fixed another regression.

commit 811230cd85 ("tcp: ipv4: initialize unicast_sock sk_pacing_rate")
was another shot in the dark.

Really, just use a proper socket per cpu, and remove the skb_orphan()
call, to re-enable flow control.

This solves a serious problem with FQ packet scheduler when used in
hostile environments, as we do not want to allocate a flow structure
for every RST packet sent in response to a spoofed packet.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/ip.h | 2 +-
include/net/netns/ipv4.h | 1 +
net/ipv4/ip_output.c | 30 +++---------------------------
net/ipv4/tcp_ipv4.c | 37 ++++++++++++++++++++++++++++++++-----
4 files changed, 37 insertions(+), 33 deletions(-)

--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -181,7 +181,7 @@ static inline __u8 ip_reply_arg_flowi_fl
return (arg->flags & IP_REPLY_ARG_NOSRCCHECK) ? FLOWI_FLAG_ANYSRC : 0;
}

-void ip_send_unicast_reply(struct net *net, struct sk_buff *skb,
+void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
const struct ip_options *sopt,
__be32 daddr, __be32 saddr,
const struct ip_reply_arg *arg,
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -52,6 +52,7 @@ struct netns_ipv4 {
struct inet_peer_base *peers;
struct tcpm_hash_bucket *tcp_metrics_hash;
unsigned int tcp_metrics_hash_log;
+ struct sock * __percpu *tcp_sk;
struct netns_frags frags;
#ifdef CONFIG_NETFILTER
struct xt_table *iptable_filter;
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1506,24 +1506,8 @@ static int ip_reply_glue_bits(void *dptr
/*
* Generic function to send a packet as reply to another packet.
* Used to send some TCP resets/acks so far.
- *
- * Use a fake percpu inet socket to avoid false sharing and contention.
*/
-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),
- .sk_pacing_rate = ~0U,
- },
- .pmtudisc = IP_PMTUDISC_WANT,
- .uc_ttl = -1,
-};
-
-void ip_send_unicast_reply(struct net *net, struct sk_buff *skb,
+void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
const struct ip_options *sopt,
__be32 daddr, __be32 saddr,
const struct ip_reply_arg *arg,
@@ -1533,9 +1517,8 @@ void ip_send_unicast_reply(struct net *n
struct ipcm_cookie ipc;
struct flowi4 fl4;
struct rtable *rt = skb_rtable(skb);
+ struct net *net = sock_net(sk);
struct sk_buff *nskb;
- struct sock *sk;
- struct inet_sock *inet;
int err;

if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
@@ -1566,15 +1549,11 @@ void ip_send_unicast_reply(struct net *n
if (IS_ERR(rt))
return;

- inet = &get_cpu_var(unicast_sock);
+ inet_sk(sk)->tos = arg->tos;

- 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;
err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
len, 0, &ipc, &rt, MSG_DONTWAIT);
@@ -1590,13 +1569,10 @@ void ip_send_unicast_reply(struct net *n
arg->csumoffset) = csum_fold(csum_add(nskb->csum,
arg->csum));
nskb->ip_summed = CHECKSUM_NONE;
- skb_orphan(nskb);
skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
ip_push_pending_frames(sk, &fl4);
}
out:
- put_cpu_var(unicast_sock);
-
ip_rt_put(rt);
}

--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -683,7 +683,8 @@ static void tcp_v4_send_reset(struct soc
arg.bound_dev_if = sk->sk_bound_dev_if;

arg.tos = ip_hdr(skb)->tos;
- ip_send_unicast_reply(net, skb, &TCP_SKB_CB(skb)->header.h4.opt,
+ ip_send_unicast_reply(*this_cpu_ptr(net->ipv4.tcp_sk),
+ skb, &TCP_SKB_CB(skb)->header.h4.opt,
ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
&arg, arg.iov[0].iov_len);

@@ -767,7 +768,8 @@ static void tcp_v4_send_ack(struct sk_bu
if (oif)
arg.bound_dev_if = oif;
arg.tos = tos;
- ip_send_unicast_reply(net, skb, &TCP_SKB_CB(skb)->header.h4.opt,
+ ip_send_unicast_reply(*this_cpu_ptr(net->ipv4.tcp_sk),
+ skb, &TCP_SKB_CB(skb)->header.h4.opt,
ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
&arg, arg.iov[0].iov_len);

@@ -2426,14 +2428,39 @@ struct proto tcp_prot = {
};
EXPORT_SYMBOL(tcp_prot);

+static void __net_exit tcp_sk_exit(struct net *net)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.tcp_sk, cpu));
+ free_percpu(net->ipv4.tcp_sk);
+}
+
static int __net_init tcp_sk_init(struct net *net)
{
+ int res, cpu;
+
+ net->ipv4.tcp_sk = alloc_percpu(struct sock *);
+ if (!net->ipv4.tcp_sk)
+ return -ENOMEM;
+
+ for_each_possible_cpu(cpu) {
+ struct sock *sk;
+
+ res = inet_ctl_sock_create(&sk, PF_INET, SOCK_RAW,
+ IPPROTO_TCP, net);
+ if (res)
+ goto fail;
+ *per_cpu_ptr(net->ipv4.tcp_sk, cpu) = sk;
+ }
net->ipv4.sysctl_tcp_ecn = 2;
return 0;
-}

-static void __net_exit tcp_sk_exit(struct net *net)
-{
+fail:
+ tcp_sk_exit(net);
+
+ return res;
}

static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)