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ipv4: tcp: get rid of ugly unicast_sock 

In commit be9f4a44e7 ("ipv4: tcp: remove per net tcp_sock")
I tried to address contention on a socket lock, but the solution
I chose was horrible :

commit 3a7c384ffd ("ipv4: tcp: unicast_sock should not land outside
of TCP stack") addressed a selinux regression.

commit 0980e56e50 ("ipv4: tcp: set unicast_sock uc_ttl to -1")
took care of another regression.

commit b5ec8eeac4 ("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>
This commit is contained in:
Eric Dumazet 2015-01-29 21:35:05 -08:00 committed by David S. Miller
parent 0d32ef8cef
commit bdbbb8527b
4 changed files with 40 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/ip.h
View File

@ -181,7 +181,7 @@ static inline __u8 ip_reply_arg_flowi_flags(const struct ip_reply_arg *arg)
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,

1
include/net/netns/ipv4.h
View File

@ -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;

30
net/ipv4/ip_output.c
View File

@ -1506,24 +1506,8 @@ 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 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 *net, struct sk_buff *skb,
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 *net, struct sk_buff *skb,
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 *net, struct sk_buff *skb,
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);
}

43
net/ipv4/tcp_ipv4.c
View File

@ -683,7 +683,8 @@ static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb)
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_buff *skb, u32 seq, u32 ack,
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);
@ -2428,14 +2430,39 @@ struct proto tcp_prot = {
};
EXPORT_SYMBOL(tcp_prot);
static int __net_init tcp_sk_init(struct net *net)
{
net->ipv4.sysctl_tcp_ecn = 2;
return 0;
}
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;
fail:
tcp_sk_exit(net);
return res;
}
static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)