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net: Replace the limit of TCP_LINGER2 with TCP_FIN_TIMEOUT_MAX

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This patch changes the behavior of TCP_LINGER2 about its limit. The
sysctl_tcp_fin_timeout used to be the limit of TCP_LINGER2 but now it's
only the default value. A new macro named TCP_FIN_TIMEOUT_MAX is added
as the limit of TCP_LINGER2, which is 2 minutes.

Since TCP_LINGER2 used sysctl_tcp_fin_timeout as the default value
and the limit in the past, the system administrator cannot set the
default value for most of sockets and let some sockets have a greater
timeout. It might be a mistake that let the sysctl to be the limit of
the TCP_LINGER2. Maybe we can add a new sysctl to set the max of
TCP_LINGER2, but FIN-WAIT-2 timeout is usually no need to be too long
and 2 minutes are legal considering TCP specs.

Changes in v3:
- Remove the new socket option and change the TCP_LINGER2 behavior so
  that the timeout can be set to value between sysctl_tcp_fin_timeout
  and 2 minutes.

Changes in v2:
- Add int overflow check for the new socket option.

Changes in v1:
- Add a new socket option to set timeout greater than
  sysctl_tcp_fin_timeout.

Signed-off-by: Cambda Zhu <cambda@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Cambda Zhu 2020-04-24 16:06:16 +08:00 committed by David S. Miller
parent a465fb1e2f
commit f0628c524f
2 changed files with 3 additions and 2 deletions
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1
include/net/tcp.h
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@ -126,6 +126,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
* to combine FIN-WAIT-2 timeout with * to combine FIN-WAIT-2 timeout with
* TIME-WAIT timer. * TIME-WAIT timer.
*/ */
#define TCP_FIN_TIMEOUT_MAX (120 * HZ) /* max TCP_LINGER2 value (two minutes) */
#define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */ #define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */
#if HZ >= 100 #if HZ >= 100

4
net/ipv4/tcp.c
View File

@ -3035,8 +3035,8 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
case TCP_LINGER2: case TCP_LINGER2:
if (val < 0) if (val < 0)
tp->linger2 = -1; tp->linger2 = -1;
else if (val > net->ipv4.sysctl_tcp_fin_timeout / HZ) else if (val > TCP_FIN_TIMEOUT_MAX / HZ)
tp->linger2 = 0; tp->linger2 = TCP_FIN_TIMEOUT_MAX;
else else
tp->linger2 = val * HZ; tp->linger2 = val * HZ;
break; break;