> On 6 Feb 2021, at 15:23, Alexander Bluhm <[email protected]> wrote:
>
> On Sat, Feb 06, 2021 at 05:04:20PM +1000, David Gwynne wrote:
>> refcnt_init starts counting at 1, while the existing code starts at 0. Do
>> the crashes stop because we never fully release all the references and
>> never free it now?
>
> You are absolutely right. I was too optimistic.
>
> Correct diff is below. It does not fix anything. Only advantage
> is that carp does not access interface group internals.
>
> bluhm
I’m not sure it should be atomic. It seems groups require their own
lock and this lock should be held while we perform if_addgroup() and
if_delgroup(). However if_creategroup() should set `ifg_refcnt’ to 1
and carp(4) should not touch groups internals.
>
> Index: net/if.c
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/sys/net/if.c,v
> retrieving revision 1.626
> diff -u -p -r1.626 if.c
> --- net/if.c 1 Feb 2021 07:43:33 -0000 1.626
> +++ net/if.c 6 Feb 2021 12:16:20 -0000
> @@ -2601,7 +2601,7 @@ if_creategroup(const char *groupname)
> return (NULL);
>
> strlcpy(ifg->ifg_group, groupname, sizeof(ifg->ifg_group));
> - ifg->ifg_refcnt = 0;
> + refcnt_init(&ifg->ifg_refcnt);
> ifg->ifg_carp_demoted = 0;
> TAILQ_INIT(&ifg->ifg_members);
> #if NPF > 0
> @@ -2642,13 +2642,17 @@ if_addgroup(struct ifnet *ifp, const cha
> if (!strcmp(ifg->ifg_group, groupname))
> break;
>
> - if (ifg == NULL && (ifg = if_creategroup(groupname)) == NULL) {
> + if (ifg == NULL)
> + ifg = if_creategroup(groupname);
> + else
> + refcnt_take(&ifg->ifg_refcnt);
> +
> + if (ifg == NULL) {
> free(ifgl, M_TEMP, sizeof(*ifgl));
> free(ifgm, M_TEMP, sizeof(*ifgm));
> return (ENOMEM);
> }
>
> - ifg->ifg_refcnt++;
> ifgl->ifgl_group = ifg;
> ifgm->ifgm_ifp = ifp;
>
> @@ -2692,7 +2696,7 @@ if_delgroup(struct ifnet *ifp, const cha
> pfi_group_change(groupname);
> #endif
>
> - if (--ifgl->ifgl_group->ifg_refcnt == 0) {
> + if (refcnt_rele(&ifgl->ifgl_group->ifg_refcnt)) {
> TAILQ_REMOVE(&ifg_head, ifgl->ifgl_group, ifg_next);
> #if NPF > 0
> pfi_detach_ifgroup(ifgl->ifgl_group);
> Index: net/if_var.h
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/sys/net/if_var.h,v
> retrieving revision 1.112
> diff -u -p -r1.112 if_var.h
> --- net/if_var.h 29 Jul 2020 12:09:31 -0000 1.112
> +++ net/if_var.h 6 Feb 2021 12:11:35 -0000
> @@ -263,7 +263,7 @@ struct ifmaddr {
>
> struct ifg_group {
> char ifg_group[IFNAMSIZ];
> - u_int ifg_refcnt;
> + struct refcnt ifg_refcnt;
> caddr_t ifg_pf_kif;
> int ifg_carp_demoted;
> TAILQ_HEAD(, ifg_member) ifg_members;
> Index: netinet/ip_carp.c
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/ip_carp.c,v
> retrieving revision 1.351
> diff -u -p -r1.351 ip_carp.c
> --- netinet/ip_carp.c 21 Jan 2021 13:18:07 -0000 1.351
> +++ netinet/ip_carp.c 6 Feb 2021 12:11:35 -0000
> @@ -786,10 +786,7 @@ carp_sysctl(int *name, u_int namelen, vo
> void
> carpattach(int n)
> {
> - struct ifg_group *ifg;
> -
> - if ((ifg = if_creategroup("carp")) != NULL)
> - ifg->ifg_refcnt++; /* keep around even if empty */
> + if_creategroup("carp"); /* keep around even if empty */
> if_clone_attach(&carp_cloner);
> carpcounters = counters_alloc(carps_ncounters);
> }
>
