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Subject[Patch v3 3/3] ipv4: Namespaceify tcp_fastopen_blackhole_timeout knob
Date
Different namespace application might require different time period in
second to disable Fastopen on active TCP sockets.

Tested:
Simulate following similar situation that the server's data gets dropped
after 3WHS.
C ---- syn-data ---> S
C <--- syn/ack ----- S
C ---- ack --------> S
S (accept & write)
C? X <- data ------ S
[retry and timeout]

And then print netstat of TCPFastOpenBlackhole, the counter increased as
expected when the firewall blackhole issue is detected and active TFO is
disabled.
# cat /proc/net/netstat | awk '{print $91}'
TCPFastOpenBlackhole
1

Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
---
include/net/netns/ipv4.h | 3 +++
net/ipv4/sysctl_net_ipv4.c | 20 +++++++++++---------
net/ipv4/tcp_fastopen.c | 28 ++++++++++------------------
net/ipv4/tcp_ipv4.c | 2 ++
4 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 66b8335..d76edde 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -132,6 +132,9 @@ struct netns_ipv4 {
int sysctl_tcp_fastopen;
struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
spinlock_t tcp_fastopen_ctx_lock;
+ unsigned int sysctl_tcp_fastopen_blackhole_timeout;
+ atomic_t tfo_active_disable_times;
+ unsigned long tfo_active_disable_stamp;

#ifdef CONFIG_NET_L3_MASTER_DEV
int sysctl_udp_l3mdev_accept;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 20e19fe..cac8dd3 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -355,11 +355,13 @@ static int proc_tfo_blackhole_detect_timeout(struct ctl_table *table,
void __user *buffer,
size_t *lenp, loff_t *ppos)
{
+ struct net *net = container_of(table->data, struct net,
+ ipv4.sysctl_tcp_fastopen_blackhole_timeout);
int ret;

ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (write && ret == 0)
- tcp_fastopen_active_timeout_reset();
+ atomic_set(&net->ipv4.tfo_active_disable_times, 0);

return ret;
}
@@ -398,14 +400,6 @@ static int proc_tcp_available_ulp(struct ctl_table *ctl,
.proc_handler = proc_dointvec
},
{
- .procname = "tcp_fastopen_blackhole_timeout_sec",
- .data = &sysctl_tcp_fastopen_blackhole_timeout,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = proc_tfo_blackhole_detect_timeout,
- .extra1 = &zero,
- },
- {
.procname = "tcp_abort_on_overflow",
.data = &sysctl_tcp_abort_on_overflow,
.maxlen = sizeof(int),
@@ -1083,6 +1077,14 @@ static int proc_tcp_available_ulp(struct ctl_table *ctl,
.maxlen = ((TCP_FASTOPEN_KEY_LENGTH * 2) + 10),
.proc_handler = proc_tcp_fastopen_key,
},
+ {
+ .procname = "tcp_fastopen_blackhole_timeout_sec",
+ .data = &init_net.ipv4.sysctl_tcp_fastopen_blackhole_timeout,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_tfo_blackhole_detect_timeout,
+ .extra1 = &zero,
+ },
#ifdef CONFIG_IP_ROUTE_MULTIPATH
{
.procname = "fib_multipath_use_neigh",
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 21783c7..f3b00a9 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -407,25 +407,16 @@ bool tcp_fastopen_defer_connect(struct sock *sk, int *err)
* TFO connection with data exchanges.
*/

-/* Default to 1hr */
-unsigned int sysctl_tcp_fastopen_blackhole_timeout __read_mostly = 60 * 60;
-static atomic_t tfo_active_disable_times __read_mostly = ATOMIC_INIT(0);
-static unsigned long tfo_active_disable_stamp __read_mostly;
-
/* Disable active TFO and record current jiffies and
* tfo_active_disable_times
*/
void tcp_fastopen_active_disable(struct sock *sk)
{
- atomic_inc(&tfo_active_disable_times);
- tfo_active_disable_stamp = jiffies;
- NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENBLACKHOLE);
-}
+ struct net *net = sock_net(sk);

-/* Reset tfo_active_disable_times to 0 */
-void tcp_fastopen_active_timeout_reset(void)
-{
- atomic_set(&tfo_active_disable_times, 0);
+ atomic_inc(&net->ipv4.tfo_active_disable_times);
+ net->ipv4.tfo_active_disable_stamp = jiffies;
+ NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE);
}

/* Calculate timeout for tfo active disable
@@ -434,17 +425,18 @@ void tcp_fastopen_active_timeout_reset(void)
*/
bool tcp_fastopen_active_should_disable(struct sock *sk)
{
- int tfo_da_times = atomic_read(&tfo_active_disable_times);
+ int tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
int multiplier;
unsigned long timeout;
+ unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;

if (!tfo_da_times)
return false;

/* Limit timout to max: 2^6 * initial timeout */
multiplier = 1 << min(tfo_da_times - 1, 6);
- timeout = multiplier * sysctl_tcp_fastopen_blackhole_timeout * HZ;
- if (time_before(jiffies, tfo_active_disable_stamp + timeout))
+ timeout = multiplier * tfo_bh_timeout * HZ;
+ if (time_before(jiffies, sock_net(sk)->ipv4.tfo_active_disable_stamp + timeout))
return true;

/* Mark check bit so we can check for successful active TFO
@@ -480,10 +472,10 @@ void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
}
}
} else if (tp->syn_fastopen_ch &&
- atomic_read(&tfo_active_disable_times)) {
+ atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
dst = sk_dst_get(sk);
if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK)))
- tcp_fastopen_active_timeout_reset();
+ atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
dst_release(dst);
}
}
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 29e042c..4b7aedb 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2474,6 +2474,8 @@ static int __net_init tcp_sk_init(struct net *net)

net->ipv4.sysctl_tcp_fastopen = TFO_CLIENT_ENABLE;
spin_lock_init(&net->ipv4.tcp_fastopen_ctx_lock);
+ net->ipv4.sysctl_tcp_fastopen_blackhole_timeout = 60 * 60;
+ atomic_set(&net->ipv4.tfo_active_disable_times, 0);

return 0;
fail:
--
1.8.3.1


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