[src/trunk]: src/sys/sys Setting a socket buffer size stops autoscaling. Add ...

[mlelstv <mlelstv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/e5c74b722e21
branches:  trunk
changeset: 944941:e5c74b722e21
user:      mlelstv <mlelstv%NetBSD.org@localhost>
date:      Sat Oct 17 09:06:15 2020 +0000

description:
Setting a socket buffer size stops autoscaling. Add a sysctl to
prevent this behaviour. The default is not changed.

diffstat:

 share/man/man7/sysctl.7 |   5 ++++-
 sys/kern/uipc_socket.c  |  22 ++++++++++++++++++----
 sys/sys/sysctl.h        |   3 ++-
 3 files changed, 24 insertions(+), 6 deletions(-)

diffs (107 lines):

diff -r 8f2296f1b170 -r e5c74b722e21 share/man/man7/sysctl.7
--- a/share/man/man7/sysctl.7   Sat Oct 17 09:04:59 2020 +0000
+++ b/share/man/man7/sysctl.7   Sat Oct 17 09:06:15 2020 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: sysctl.7,v 1.149 2020/09/11 15:16:48 roy Exp $
+.\"    $NetBSD: sysctl.7,v 1.150 2020/10/17 09:06:15 mlelstv Exp $
 .\"
 .\" Copyright (c) 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -359,6 +359,7 @@
 .It kern.sbmax integer yes
 .It kern.sched node    not applicable
 .It kern.securelevel   integer raise only
+.It kern.sofixedbuf    boolean yes
 .It kern.somaxkva      integer yes
 .It kern.sooptions     integer yes
 .It kern.synchronized_io       integer no
@@ -1206,6 +1207,8 @@
 See
 .Xr sched 3 .
 .El
+.It Li kern.sofixedbuf ( Dv KERN_SOFIXEDBUF )
+Prevent socket buffer autoscaling when a size is set with SO_SNDBUF or SO_RCVBUF.
 .It Li kern.somaxkva ( Dv KERN_SOMAXKVA )
 Maximum amount of kernel memory to be used for socket buffers in bytes.
 .It Li kern.sooptions
diff -r 8f2296f1b170 -r e5c74b722e21 sys/kern/uipc_socket.c
--- a/sys/kern/uipc_socket.c    Sat Oct 17 09:04:59 2020 +0000
+++ b/sys/kern/uipc_socket.c    Sat Oct 17 09:06:15 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uipc_socket.c,v 1.291 2020/08/26 22:54:30 christos Exp $       */
+/*     $NetBSD: uipc_socket.c,v 1.292 2020/10/17 09:06:15 mlelstv Exp $        */
 
 /*
  * Copyright (c) 2002, 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -71,7 +71,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uipc_socket.c,v 1.291 2020/08/26 22:54:30 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uipc_socket.c,v 1.292 2020/10/17 09:06:15 mlelstv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_compat_netbsd.h"
@@ -166,6 +166,11 @@
 static int socurkva;
 static kcondvar_t socurkva_cv;
 
+#ifndef SOFIXEDBUF
+#define SOFIXEDBUF true
+#endif
+bool sofixedbuf = SOFIXEDBUF;
+
 static kauth_listener_t socket_listener;
 
 #define        SOCK_LOAN_CHUNK         65536
@@ -1798,7 +1803,8 @@
                                error = ENOBUFS;
                                break;
                        }
-                       so->so_snd.sb_flags &= ~SB_AUTOSIZE;
+                       if (sofixedbuf)
+                               so->so_snd.sb_flags &= ~SB_AUTOSIZE;
                        break;
 
                case SO_RCVBUF:
@@ -1806,7 +1812,8 @@
                                error = ENOBUFS;
                                break;
                        }
-                       so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
+                       if (sofixedbuf)
+                               so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
                        break;
 
                /*
@@ -2540,6 +2547,13 @@
 
        sysctl_createv(&socket_sysctllog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
+                      CTLTYPE_BOOL, "sofixedbuf",
+                      SYSCTL_DESCR("Prevent scaling of fixed socket buffers"),
+                      NULL, 0, &sofixedbuf, 0,
+                      CTL_KERN, KERN_SOFIXEDBUF, CTL_EOL);
+
+       sysctl_createv(&socket_sysctllog, 0, NULL, NULL,
+                      CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "sbmax",
                       SYSCTL_DESCR("Maximum socket buffer size"),
                       sysctl_kern_sbmax, 0, NULL, 0,
diff -r 8f2296f1b170 -r e5c74b722e21 sys/sys/sysctl.h
--- a/sys/sys/sysctl.h  Sat Oct 17 09:04:59 2020 +0000
+++ b/sys/sys/sysctl.h  Sat Oct 17 09:06:15 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sysctl.h,v 1.230 2019/05/31 23:01:39 kamil Exp $       */
+/*     $NetBSD: sysctl.h,v 1.231 2020/10/17 09:06:15 mlelstv Exp $     */
 
 /*
  * Copyright (c) 1989, 1993
@@ -274,6 +274,7 @@
 #define        KERN_SYSVIPC            82      /* node: SysV IPC parameters */
 #define        KERN_BOOTTIME           83      /* struct: time kernel was booted */
 #define        KERN_EVCNT              84      /* struct: evcnts */
+#define        KERN_SOFIXEDBUF         85      /* bool: fixed socket buffer sizes */
 
 /*
  *  KERN_CLOCKRATE structure