[src/trunk]: src/sys/net wg: Fix detach logic.

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

details:   https://anonhg.NetBSD.org/src/rev/6be8d2b2491a
branches:  trunk
changeset: 976155:6be8d2b2491a
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Sep 13 17:18:54 2020 +0000

description:
wg: Fix detach logic.

Not tested but this should be less of a rake to step on if anyone
made an unloadable wg module.

diffstat:

 sys/net/if_wg.c |  83 ++++++++++++++++++++++++++++++++------------------------
 1 files changed, 48 insertions(+), 35 deletions(-)

diffs (167 lines):

diff -r ed9b0477dc61 -r 6be8d2b2491a sys/net/if_wg.c
--- a/sys/net/if_wg.c   Sun Sep 13 17:18:13 2020 +0000
+++ b/sys/net/if_wg.c   Sun Sep 13 17:18:54 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_wg.c,v 1.58 2020/09/13 17:18:13 riastradh Exp $     */
+/*     $NetBSD: if_wg.c,v 1.59 2020/09/13 17:18:54 riastradh Exp $     */
 
 /*
  * Copyright (C) Ryota Ozaki <ozaki.ryota%gmail.com@localhost>
@@ -41,7 +41,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_wg.c,v 1.58 2020/09/13 17:18:13 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_wg.c,v 1.59 2020/09/13 17:18:54 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -144,8 +144,6 @@
  *   - Data messages are always sent via a stable session
  *
  * Locking notes:
- * - wg interfaces (struct wg_softc, wg) is listed in wg_softcs.list and
- *   protected by wg_softcs.lock
  * - Each wg has a mutex(9) wg_lock, and a rwlock(9) wg_rwlock
  *   - Changes to the peer list are serialized by wg_lock
  *   - The peer list may be read with pserialize(9) and psref(9)
@@ -780,11 +778,7 @@
 /*
  * Global variables
  */
-LIST_HEAD(wg_sclist, wg_softc);
-static struct {
-       struct wg_sclist list;
-       kmutex_t lock;
-} wg_softcs __cacheline_aligned;
+static volatile unsigned wg_count __cacheline_aligned;
 
 struct psref_class *wg_psref_class __read_mostly;
 
@@ -811,9 +805,6 @@
 
        wg_psref_class = psref_class_create("wg", IPL_SOFTNET);
 
-       mutex_init(&wg_softcs.lock, MUTEX_DEFAULT, IPL_NONE);
-       LIST_INIT(&wg_softcs.list);
-
        if_clone_attach(&wg_cloner);
 }
 
@@ -848,23 +839,49 @@
 }
 
 static int
+wg_count_inc(void)
+{
+       unsigned o, n;
+
+       do {
+               o = atomic_load_relaxed(&wg_count);
+               if (o == UINT_MAX)
+                       return ENFILE;
+               n = o + 1;
+       } while (atomic_cas_uint(&wg_count, o, n) != o);
+
+       return 0;
+}
+
+static void
+wg_count_dec(void)
+{
+       unsigned c __diagused;
+
+       c = atomic_dec_uint_nv(&wg_count);
+       KASSERT(c != UINT_MAX);
+}
+
+static int
 wgdetach(void)
 {
-       int error = 0;
-
-       mutex_enter(&wg_softcs.lock);
-       if (!LIST_EMPTY(&wg_softcs.list)) {
-               mutex_exit(&wg_softcs.lock);
-               error = EBUSY;
+
+       /* Prevent new interface creation.  */
+       if_clone_detach(&wg_cloner);
+
+       /* Check whether there are any existing interfaces.  */
+       if (atomic_load_relaxed(&wg_count)) {
+               /* Back out -- reattach the cloner.  */
+               if_clone_attach(&wg_cloner);
+               return EBUSY;
        }
 
-       if (error == 0) {
-               psref_class_destroy(wg_psref_class);
-
-               if_clone_detach(&wg_cloner);
-       }
-
-       return error;
+       /* No interfaces left.  Nuke it.  */
+       workqueue_destroy(wg_wq);
+       pktq_destroy(wg_pktq);
+       psref_class_destroy(wg_psref_class);
+
+       return 0;
 }
 
 static void
@@ -3555,6 +3572,10 @@
 
        wg_guarantee_initialized();
 
+       error = wg_count_inc();
+       if (error)
+               return error;
+
        wg = kmem_zalloc(sizeof(*wg), KM_SLEEP);
 
        if_initname(&wg->wg_if, ifc->ifc_name, unit);
@@ -3593,16 +3614,9 @@
        if (error)
                goto fail3;
 
-       mutex_enter(&wg_softcs.lock);
-       LIST_INSERT_HEAD(&wg_softcs.list, wg, wg_list);
-       mutex_exit(&wg_softcs.lock);
-
        return 0;
 
 fail4: __unused
-       mutex_enter(&wg_softcs.lock);
-       LIST_REMOVE(wg, wg_list);
-       mutex_exit(&wg_softcs.lock);
        wg_if_detach(wg);
 fail3: wg_destroy_all_peers(wg);
 #ifdef INET6
@@ -3640,6 +3654,7 @@
        thmap_destroy(wg->wg_peers_bypubkey);
        PSLIST_DESTROY(&wg->wg_peers);
        kmem_free(wg, sizeof(*wg));
+       wg_count_dec();
        return error;
 }
 
@@ -3655,9 +3670,6 @@
        }
 #endif
 
-       mutex_enter(&wg_softcs.lock);
-       LIST_REMOVE(wg, wg_list);
-       mutex_exit(&wg_softcs.lock);
        wg_if_detach(wg);
        wg_destroy_all_peers(wg);
 #ifdef INET6
@@ -3693,6 +3705,7 @@
        thmap_destroy(wg->wg_peers_bypubkey);
        PSLIST_DESTROY(&wg->wg_peers);
        kmem_free(wg, sizeof(*wg));
+       wg_count_dec();
 
        return 0;
 }