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Commit bdbbb852 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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ipv4: tcp: get rid of ugly unicast_sock 



In commit be9f4a44 ("ipv4: tcp: remove per net tcp_sock")
I tried to address contention on a socket lock, but the solution
I chose was horrible :

commit 3a7c384f ("ipv4: tcp: unicast_sock should not land outside
of TCP stack") addressed a selinux regression.

commit 0980e56e ("ipv4: tcp: set unicast_sock uc_ttl to -1")
took care of another regression.

commit b5ec8eea ("ipv4: fix ip_send_skb()") fixed another regression.

commit 811230cd ("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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0d32ef8c

include/net/ip.h

+1 −1
Original line number Diff line number Diff line
@@ -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,

include/net/netns/ipv4.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

net/ipv4/ip_output.c

+3 −27
Original line number Diff line number Diff line
@@ -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);

}

net/ipv4/tcp_ipv4.c

+32 −5
Original line number Diff line number Diff line
@@ -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 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)