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Message-Id: <20210809185314.38187-2-tom@herbertland.com>
Date: Mon, 9 Aug 2021 11:53:12 -0700
From: Tom Herbert <tom@...bertland.com>
To: netdev@...r.kernel.org, davem@...emloft.net, brakmo@...com,
ycheng@...gle.com, eric.dumazet@...il.com, a.e.azimov@...il.com
Cc: Tom Herbert <tom@...bertland.com>
Subject: [RFC PATCH net-next 1/3] txhash: Make rethinking txhash behavior configurable via sysctl
Add a per ns sysctl that controls the txhash rethink behavior,
sk_rethink_txhash. This sysctl value is a mask rethink modes that are:
rethink at negative advice, rethink at SYN RTO, and rethink at non-SYN
RTO. A value of zero disables hash rethink. The default mask is set
to rethink with all three modes (retains current default behavior)
---
include/net/netns/core.h | 2 ++
include/net/sock.h | 26 +++++++++++++++++---------
include/uapi/linux/socket.h | 13 +++++++++++++
net/core/net_namespace.c | 6 ++++++
net/core/sysctl_net_core.c | 7 +++++++
net/ipv4/tcp_input.c | 2 +-
net/ipv4/tcp_timer.c | 5 ++++-
7 files changed, 50 insertions(+), 11 deletions(-)
diff --git a/include/net/netns/core.h b/include/net/netns/core.h
index 36c2d998a43c..503f43bfc1d3 100644
--- a/include/net/netns/core.h
+++ b/include/net/netns/core.h
@@ -11,6 +11,8 @@ struct netns_core {
int sysctl_somaxconn;
+ unsigend int sysctl_txrehash_mode;
+
#ifdef CONFIG_PROC_FS
int __percpu *sock_inuse;
struct prot_inuse __percpu *prot_inuse;
diff --git a/include/net/sock.h b/include/net/sock.h
index 6e761451c927..6ef5314e8eed 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -577,6 +577,12 @@ static inline bool sk_user_data_is_nocopy(const struct sock *sk)
__tmp | SK_USER_DATA_NOCOPY); \
})
+static inline
+struct net *sock_net(const struct sock *sk)
+{
+ return read_pnet(&sk->sk_net);
+}
+
/*
* SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK
* or not whether his port will be reused by someone else. SK_FORCE_REUSE
@@ -1940,12 +1946,20 @@ static inline void sk_set_txhash(struct sock *sk)
WRITE_ONCE(sk->sk_txhash, net_tx_rndhash());
}
-static inline bool sk_rethink_txhash(struct sock *sk)
+static inline bool sk_rethink_txhash(struct sock *sk, unsigned int level)
{
- if (sk->sk_txhash) {
+ unsigned int rehash_mode;
+
+ if (!sk->sk_txhash)
+ return false;
+
+ rehash_mode = READ_ONCE(sock_net(sk)->core.sysctl_txrehash_mode);
+
+ if (level & rehash_mode) {
sk_set_txhash(sk);
return true;
}
+
return false;
}
@@ -1986,7 +2000,7 @@ static inline void __dst_negative_advice(struct sock *sk)
static inline void dst_negative_advice(struct sock *sk)
{
- sk_rethink_txhash(sk);
+ sk_rethink_txhash(sk, SOCK_TXREHASH_MODE_NEG_ADVICE);
__dst_negative_advice(sk);
}
@@ -2591,12 +2605,6 @@ static inline void sk_eat_skb(struct sock *sk, struct sk_buff *skb)
__kfree_skb(skb);
}
-static inline
-struct net *sock_net(const struct sock *sk)
-{
- return read_pnet(&sk->sk_net);
-}
-
static inline
void sock_net_set(struct sock *sk, struct net *net)
{
diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index eb0a9a5b6e71..2c2cef795a9b 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h
@@ -31,4 +31,17 @@ struct __kernel_sockaddr_storage {
#define SOCK_BUF_LOCK_MASK (SOCK_SNDBUF_LOCK | SOCK_RCVBUF_LOCK)
+#define SOCK_TXREHASH_MODE_DISABLE 0
+
+/* Flag bits for individual rehash function modes */
+#define SOCK_TXREHASH_MODE_NEG_ADVICE 0x1
+#define SOCK_TXREHASH_MODE_SYN_RTO 0x2
+#define SOCK_TXREHASH_MODE_RTO 0x4
+
+#define SOCK_TXREHASH_MODE_DEFAULT -1U
+
+#define SOCK_TXREHASH_MODE_MASK (SOCK_TXREHASH_MODE_NEG_ADVICE | \
+ SOCK_TXREHASH_MODE_SYN_RTO | \
+ SOCK_TXREHASH_MODE_RTO)
+
#endif /* _UAPI_LINUX_SOCKET_H */
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 9b5a767eddd5..03d3767e6728 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -366,6 +366,12 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
static int __net_init net_defaults_init_net(struct net *net)
{
net->core.sysctl_somaxconn = SOMAXCONN;
+
+ /* Default rethink mode is aggrssive (i.e. rethink on first RTO) */
+ net->core.sysctl_txrehash_mode = SOCK_TXREHASH_MODE_NEG_ADVICE |
+ SOCK_TXREHASH_MODE_SYN_RTO |
+ SOCK_TXREHASH_MODE_RTO;
+
return 0;
}
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index c8496c1142c9..7e828a892bf5 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -592,6 +592,13 @@ static struct ctl_table netns_core_table[] = {
.extra1 = SYSCTL_ZERO,
.proc_handler = proc_dointvec_minmax
},
+ {
+ .procname = "txrehash_mode",
+ .data = &init_net.core.sysctl_txrehash_mode,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
{ }
};
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3f7bd7ae7d7a..08eeb2523393 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4442,7 +4442,7 @@ static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
* DSACK state and change the txhash to re-route speculatively.
*/
if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq &&
- sk_rethink_txhash(sk))
+ sk_rethink_txhash(sk, SOCK_TXREHASH_MODE_RTO))
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDUPLICATEDATAREHASH);
}
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 20cf4a98c69d..53ae43ab5ebe 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -234,6 +234,7 @@ static int tcp_write_timeout(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
struct net *net = sock_net(sk);
bool expired = false, do_reset;
+ unsigned int rehash_mode;
int retry_until;
if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
@@ -241,6 +242,7 @@ static int tcp_write_timeout(struct sock *sk)
__dst_negative_advice(sk);
retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries;
expired = icsk->icsk_retransmits >= retry_until;
+ rehash_mode = SOCK_TXREHASH_MODE_SYN_RTO;
} else {
if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) {
/* Black hole detection */
@@ -260,6 +262,7 @@ static int tcp_write_timeout(struct sock *sk)
if (tcp_out_of_resources(sk, do_reset))
return 1;
}
+ rehash_mode = SOCK_TXREHASH_MODE_RTO;
}
if (!expired)
expired = retransmits_timed_out(sk, retry_until,
@@ -277,7 +280,7 @@ static int tcp_write_timeout(struct sock *sk)
return 1;
}
- if (sk_rethink_txhash(sk)) {
+ if (sk_rethink_txhash(sk, rehash_mode)) {
tp->timeout_rehash++;
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH);
}
--
2.25.1
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