From 58d607d3e52f2b15902f58a1161da9fb3b0f6d47 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Tue, 15 Sep 2015 15:24:20 -0700
Subject: [PATCH] tcp: provide skb->hash to synack packets
In commit b73c3d0e4f0e ("net: Save TX flow hash in sock and set in skbuf
on xmit"), Tom provided a l4 hash to most outgoing TCP packets.
We'd like to provide one as well for SYNACK packets, so that all packets
of a given flow share same txhash, to later enable bonding driver to
also use skb->hash to perform slave selection.
Note that a SYNACK retransmit shuffles the tx hash, as Tom did
in commit 265f94ff54d62 ("net: Recompute sk_txhash on negative routing
advice") for established sockets.
This has nice effect making TCP flows resilient to some kind of black
holes, even at connection establish phase.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <tom@herbertland.com>
Cc: Mahesh Bandewar <maheshb@google.com>
Acked-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
include/linux/tcp.h | 1 +
include/net/sock.h | 12 ++++++++----
net/ipv4/tcp_input.c | 1 +
net/ipv4/tcp_ipv4.c | 2 +-
net/ipv4/tcp_output.c | 2 ++
net/ipv6/tcp_ipv6.c | 2 +-
6 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 48c3696e86457..937b97893d5f4 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -113,6 +113,7 @@ struct tcp_request_sock {
struct inet_request_sock req;
const struct tcp_request_sock_ops *af_specific;
bool tfo_listener;
+ u32 txhash;
u32 rcv_isn;
u32 snt_isn;
u32 snt_synack; /* synack sent time */
diff --git a/include/net/sock.h b/include/net/sock.h
index 7aa78440559a4..94dff7f566f5c 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1654,12 +1654,16 @@ static inline void sock_graft(struct sock *sk, struct socket *parent)
kuid_t sock_i_uid(struct sock *sk);
unsigned long sock_i_ino(struct sock *sk);
-static inline void sk_set_txhash(struct sock *sk)
+static inline u32 net_tx_rndhash(void)
{
- sk->sk_txhash = prandom_u32();
+ u32 v = prandom_u32();
+
+ return v ?: 1;
+}
- if (unlikely(!sk->sk_txhash))
- sk->sk_txhash = 1;
+static inline void sk_set_txhash(struct sock *sk)
+{
+ sk->sk_txhash = net_tx_rndhash();
}
static inline void sk_rethink_txhash(struct sock *sk)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a8f515bb19c4b..a62e9c76d485f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6228,6 +6228,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
}
tcp_rsk(req)->snt_isn = isn;
+ tcp_rsk(req)->txhash = net_tx_rndhash();
tcp_openreq_init_rwin(req, sk, dst);
fastopen = !want_cookie &&
tcp_try_fastopen(sk, skb, req, &foc, dst);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 93898e093d4e6..d671d742a2398 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1276,8 +1276,8 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
newinet->mc_index = inet_iif(skb);
newinet->mc_ttl = ip_hdr(skb)->ttl;
newinet->rcv_tos = ip_hdr(skb)->tos;
+ newsk->sk_txhash = tcp_rsk(req)->txhash;
inet_csk(newsk)->icsk_ext_hdr_len = 0;
- sk_set_txhash(newsk);
if (inet_opt)
inet_csk(newsk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
newinet->inet_id = newtp->write_seq ^ jiffies;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f9a8a12b62ee6..d0ad3554c3332 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2987,6 +2987,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
rcu_read_lock();
md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
#endif
+ skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
foc) + sizeof(*th);
@@ -3505,6 +3506,7 @@ int tcp_rtx_synack(struct sock *sk, struct request_sock *req)
struct flowi fl;
int res;
+ tcp_rsk(req)->txhash = net_tx_rndhash();
res = af_ops->send_synack(sk, NULL, &fl, req, 0, NULL);
if (!res) {
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 97d9314ea3611..f9c0e26406710 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1090,7 +1090,7 @@ static struct sock *tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
newsk->sk_v6_rcv_saddr = ireq->ir_v6_loc_addr;
newsk->sk_bound_dev_if = ireq->ir_iif;
- sk_set_txhash(newsk);
+ newsk->sk_txhash = tcp_rsk(req)->txhash;
/* Now IPv6 options...
--
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