The branch main has been updated by glebius:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=d74b7baeb0d419fce46994075b6ccf944a0fae9a

commit d74b7baeb0d419fce46994075b6ccf944a0fae9a
Author:     Gleb Smirnoff <[email protected]>
AuthorDate: 2021-12-04 17:49:36 +0000
Commit:     Gleb Smirnoff <[email protected]>
CommitDate: 2021-12-06 17:32:31 +0000

    ifnet_byindex() actually requires network epoch
    
    Sweep over potentially unsafe calls to ifnet_byindex() and wrap them
    in epoch.  Most of the code touched remains unsafe, as the returned
    pointer is being used after epoch exit.  Mark that with a comment.
    
    Validate the index argument inside the function, reducing argument
    validation requirement from the callers and making V_if_index
    private to if.c.
    
    Reviewed by:            melifaro
    Differential revision:  https://reviews.freebsd.org/D33263
---
 sys/dev/hyperv/netvsc/if_hn.c |  6 ++++
 sys/net/if.c                  | 16 ++++------
 sys/net/if_var.h              | 10 +++---
 sys/netinet/igmp.c            |  8 ++---
 sys/netinet/in_mcast.c        | 49 +++++++++++++---------------
 sys/netinet/udp_usrreq.c      | 11 ++++---
 sys/netinet6/in6_mcast.c      | 74 +++++++++++++++++++++++++++----------------
 sys/netinet6/ip6_mroute.c     |  9 ++++--
 sys/netinet6/ip6_output.c     |  6 ++--
 sys/netinet6/mld6.c           | 10 ++----
 sys/netinet6/nd6_rtr.c        | 21 ++++++------
 sys/netinet6/scope6.c         | 47 +++++++++++++++++----------
 12 files changed, 147 insertions(+), 120 deletions(-)

diff --git a/sys/dev/hyperv/netvsc/if_hn.c b/sys/dev/hyperv/netvsc/if_hn.c
index de464662c2ef..025baaa60152 100644
--- a/sys/dev/hyperv/netvsc/if_hn.c
+++ b/sys/dev/hyperv/netvsc/if_hn.c
@@ -4736,11 +4736,13 @@ hn_vflist_sysctl(SYSCTL_HANDLER_ARGS)
 
        first = true;
        for (i = 0; i < hn_vfmap_size; ++i) {
+               struct epoch_tracker et;
                struct ifnet *ifp;
 
                if (hn_vfmap[i] == NULL)
                        continue;
 
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(i);
                if (ifp != NULL) {
                        if (first)
@@ -4749,6 +4751,7 @@ hn_vflist_sysctl(SYSCTL_HANDLER_ARGS)
                                sbuf_printf(sb, " %s", ifp->if_xname);
                        first = false;
                }
+               NET_EPOCH_EXIT(et);
        }
 
        rm_runlock(&hn_vfmap_lock, &pt);
@@ -4778,12 +4781,14 @@ hn_vfmap_sysctl(SYSCTL_HANDLER_ARGS)
 
        first = true;
        for (i = 0; i < hn_vfmap_size; ++i) {
+               struct epoch_tracker et;
                struct ifnet *ifp, *hn_ifp;
 
                hn_ifp = hn_vfmap[i];
                if (hn_ifp == NULL)
                        continue;
 
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(i);
                if (ifp != NULL) {
                        if (first) {
@@ -4795,6 +4800,7 @@ hn_vfmap_sysctl(SYSCTL_HANDLER_ARGS)
                        }
                        first = false;
                }
+               NET_EPOCH_EXIT(et);
        }
 
        rm_runlock(&hn_vfmap_lock, &pt);
diff --git a/sys/net/if.c b/sys/net/if.c
index ad6d0bcf827a..87c3e4af4380 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -343,9 +343,11 @@ MALLOC_DEFINE(M_IFADDR, "ifaddr", "interface address");
 MALLOC_DEFINE(M_IFMADDR, "ether_multi", "link-level multicast address");
 
 struct ifnet *
-ifnet_byindex(u_short idx)
+ifnet_byindex(u_int idx)
 {
 
+       NET_EPOCH_ASSERT();
+
        if (__predict_false(idx > V_if_index))
                return (NULL);
 
@@ -353,12 +355,10 @@ ifnet_byindex(u_short idx)
 }
 
 struct ifnet *
-ifnet_byindex_ref(u_short idx)
+ifnet_byindex_ref(u_int idx)
 {
        struct ifnet *ifp;
 
-       NET_EPOCH_ASSERT();
-
        ifp = ifnet_byindex(idx);
        if (ifp == NULL || (ifp->if_flags & IFF_DYING))
                return (NULL);
@@ -679,9 +679,7 @@ if_free(struct ifnet *ifp)
         */
        CURVNET_SET_QUIET(ifp->if_vnet);
        IFNET_WLOCK();
-       KASSERT(ifp == ifnet_byindex(ifp->if_index),
-           ("%s: freeing unallocated ifnet", ifp->if_xname));
-
+       MPASS(V_ifindex_table[ifp->if_index] == ifp);
        ifindex_free(ifp->if_index);
        IFNET_WUNLOCK();
 
@@ -831,9 +829,7 @@ if_attach_internal(struct ifnet *ifp, int vmove, struct 
if_clone *ifc)
        struct sockaddr_dl *sdl;
        struct ifaddr *ifa;
 
-       if (ifp->if_index == 0 || ifp != ifnet_byindex(ifp->if_index))
-               panic ("%s: BUG: if_attach called without if_alloc'd input()\n",
-                   ifp->if_xname);
+       MPASS(V_ifindex_table[ifp->if_index] == ifp);
 
 #ifdef VIMAGE
        ifp->if_vnet = curvnet;
diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index a0739fd6b76b..1647eb351db3 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -613,12 +613,12 @@ extern    struct sx ifnet_sxlock;
 #define        IFNET_RUNLOCK()         sx_sunlock(&ifnet_sxlock)
 
 /*
- * Look up an ifnet given its index; the _ref variant also acquires a
- * reference that must be freed using if_rele().  It is almost always a bug
- * to call ifnet_byindex() instead of ifnet_byindex_ref().
+ * Look up an ifnet given its index.  The returned value protected from
+ * being freed by the network epoch.  The _ref variant also acquires a
+ * reference that must be freed using if_rele().
  */
-struct ifnet   *ifnet_byindex(u_short idx);
-struct ifnet   *ifnet_byindex_ref(u_short idx);
+struct ifnet   *ifnet_byindex(u_int);
+struct ifnet   *ifnet_byindex_ref(u_int);
 
 /*
  * Given the index, ifaddr_byindex() returns the one and only
diff --git a/sys/netinet/igmp.c b/sys/netinet/igmp.c
index e7636330d267..58d66ebafe64 100644
--- a/sys/netinet/igmp.c
+++ b/sys/netinet/igmp.c
@@ -482,6 +482,7 @@ out_locked:
 static int
 sysctl_igmp_ifinfo(SYSCTL_HANDLER_ARGS)
 {
+       struct epoch_tracker     et;
        int                     *name;
        int                      error;
        u_int                    namelen;
@@ -504,14 +505,11 @@ sysctl_igmp_ifinfo(SYSCTL_HANDLER_ARGS)
        IN_MULTI_LIST_LOCK();
        IGMP_LOCK();
 
-       if (name[0] <= 0 || name[0] > V_if_index) {
-               error = ENOENT;
-               goto out_locked;
-       }
-
        error = ENOENT;
 
+       NET_EPOCH_ENTER(et);
        ifp = ifnet_byindex(name[0]);
+       NET_EPOCH_EXIT(et);
        if (ifp == NULL)
                goto out_locked;
 
diff --git a/sys/netinet/in_mcast.c b/sys/netinet/in_mcast.c
index 6ac81aa98e44..3f25471f0858 100644
--- a/sys/netinet/in_mcast.c
+++ b/sys/netinet/in_mcast.c
@@ -1376,6 +1376,7 @@ in_leavegroup_locked(struct in_multi *inm, /*const*/ 
struct in_mfilter *imf)
 static int
 inp_block_unblock_source(struct inpcb *inp, struct sockopt *sopt)
 {
+       struct epoch_tracker             et;
        struct group_source_req          gsr;
        sockunion_t                     *gsa, *ssa;
        struct ifnet                    *ifp;
@@ -1414,8 +1415,6 @@ inp_block_unblock_source(struct inpcb *inp, struct 
sockopt *sopt)
                ssa->sin.sin_addr = mreqs.imr_sourceaddr;
 
                if (!in_nullhost(mreqs.imr_interface)) {
-                       struct epoch_tracker et;
-
                        NET_EPOCH_ENTER(et);
                        INADDR_TO_IFP(mreqs.imr_interface, ifp);
                        /* XXXGL: ifref? */
@@ -1445,10 +1444,11 @@ inp_block_unblock_source(struct inpcb *inp, struct 
sockopt *sopt)
                    ssa->sin.sin_len != sizeof(struct sockaddr_in))
                        return (EINVAL);
 
-               if (gsr.gsr_interface == 0 || V_if_index < gsr.gsr_interface)
-                       return (EADDRNOTAVAIL);
-
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(gsr.gsr_interface);
+               NET_EPOCH_EXIT(et);
+               if (ifp == NULL)
+                       return (EADDRNOTAVAIL);
 
                if (sopt->sopt_name == MCAST_BLOCK_SOURCE)
                        doblock = 1;
@@ -1624,6 +1624,7 @@ inp_freemoptions(struct ip_moptions *imo)
 static int
 inp_get_source_filters(struct inpcb *inp, struct sockopt *sopt)
 {
+       struct epoch_tracker     et;
        struct __msfilterreq     msfr;
        sockunion_t             *gsa;
        struct ifnet            *ifp;
@@ -1649,10 +1650,9 @@ inp_get_source_filters(struct inpcb *inp, struct sockopt 
*sopt)
        if (error)
                return (error);
 
-       if (msfr.msfr_ifindex == 0 || V_if_index < msfr.msfr_ifindex)
-               return (EINVAL);
-
+       NET_EPOCH_ENTER(et);
        ifp = ifnet_byindex(msfr.msfr_ifindex);
+       NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifnet pointer left */
        if (ifp == NULL)
                return (EINVAL);
 
@@ -2026,11 +2026,11 @@ inp_join_group(struct inpcb *inp, struct sockopt *sopt)
                if (!IN_MULTICAST(ntohl(gsa->sin.sin_addr.s_addr)))
                        return (EINVAL);
 
-               if (gsr.gsr_interface == 0 || V_if_index < gsr.gsr_interface)
-                       return (EADDRNOTAVAIL);
                NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex_ref(gsr.gsr_interface);
                NET_EPOCH_EXIT(et);
+               if (ifp == NULL)
+                       return (EADDRNOTAVAIL);
                break;
 
        default:
@@ -2243,6 +2243,7 @@ out_inp_unlocked:
 static int
 inp_leave_group(struct inpcb *inp, struct sockopt *sopt)
 {
+       struct epoch_tracker             et;
        struct group_source_req          gsr;
        struct ip_mreq_source            mreqs;
        sockunion_t                     *gsa, *ssa;
@@ -2304,8 +2305,6 @@ inp_leave_group(struct inpcb *inp, struct sockopt *sopt)
                 * using an IPv4 address as a key is racy.
                 */
                if (!in_nullhost(mreqs.imr_interface)) {
-                       struct epoch_tracker et;
-
                        NET_EPOCH_ENTER(et);
                        INADDR_TO_IFP(mreqs.imr_interface, ifp);
                        /* XXXGL ifref? */
@@ -2340,11 +2339,9 @@ inp_leave_group(struct inpcb *inp, struct sockopt *sopt)
                                return (EINVAL);
                }
 
-               if (gsr.gsr_interface == 0 || V_if_index < gsr.gsr_interface)
-                       return (EADDRNOTAVAIL);
-
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(gsr.gsr_interface);
-
+               NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifp */
                if (ifp == NULL)
                        return (EADDRNOTAVAIL);
                break;
@@ -2481,13 +2478,17 @@ inp_set_multicast_if(struct inpcb *inp, struct sockopt 
*sopt)
                if (error)
                        return (error);
 
-               if (mreqn.imr_ifindex < 0 || V_if_index < mreqn.imr_ifindex)
+               if (mreqn.imr_ifindex < 0)
                        return (EINVAL);
 
                if (mreqn.imr_ifindex == 0) {
                        ifp = NULL;
                } else {
+                       struct epoch_tracker et;
+
+                       NET_EPOCH_ENTER(et);
                        ifp = ifnet_byindex(mreqn.imr_ifindex);
+                       NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifp */
                        if (ifp == NULL)
                                return (EADDRNOTAVAIL);
                }
@@ -2536,6 +2537,7 @@ inp_set_multicast_if(struct inpcb *inp, struct sockopt 
*sopt)
 static int
 inp_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
 {
+       struct epoch_tracker     et;
        struct __msfilterreq     msfr;
        sockunion_t             *gsa;
        struct ifnet            *ifp;
@@ -2566,10 +2568,9 @@ inp_set_source_filters(struct inpcb *inp, struct sockopt 
*sopt)
 
        gsa->sin.sin_port = 0;  /* ignore port */
 
-       if (msfr.msfr_ifindex == 0 || V_if_index < msfr.msfr_ifindex)
-               return (EADDRNOTAVAIL);
-
+       NET_EPOCH_ENTER(et);
        ifp = ifnet_byindex(msfr.msfr_ifindex);
+       NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifp */
        if (ifp == NULL)
                return (EADDRNOTAVAIL);
 
@@ -2881,13 +2882,6 @@ sysctl_ip_mcast_filters(SYSCTL_HANDLER_ARGS)
        if (namelen != 2)
                return (EINVAL);
 
-       ifindex = name[0];
-       if (ifindex <= 0 || ifindex > V_if_index) {
-               CTR2(KTR_IGMPV3, "%s: ifindex %u out of range",
-                   __func__, ifindex);
-               return (ENOENT);
-       }
-
        group.s_addr = name[1];
        if (!IN_MULTICAST(ntohl(group.s_addr))) {
                CTR2(KTR_IGMPV3, "%s: group 0x%08x is not multicast",
@@ -2895,6 +2889,7 @@ sysctl_ip_mcast_filters(SYSCTL_HANDLER_ARGS)
                return (EINVAL);
        }
 
+       ifindex = name[0];
        NET_EPOCH_ENTER(et);
        ifp = ifnet_byindex(ifindex);
        if (ifp == NULL) {
diff --git a/sys/netinet/udp_usrreq.c b/sys/netinet/udp_usrreq.c
index 237287fef1e6..fe5327b3bd3c 100644
--- a/sys/netinet/udp_usrreq.c
+++ b/sys/netinet/udp_usrreq.c
@@ -1100,15 +1100,16 @@ udp_v4mapped_pktinfo(struct cmsghdr *cm, struct 
sockaddr_in * src,
                return (EINVAL);
 
        /* Validate the interface index if specified. */
-       if (pktinfo->ipi6_ifindex > V_if_index)
-               return (ENXIO);
-
-       ifp = NULL;
        if (pktinfo->ipi6_ifindex) {
+               struct epoch_tracker et;
+
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(pktinfo->ipi6_ifindex);
+               NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifp */
                if (ifp == NULL)
                        return (ENXIO);
-       }
+       } else
+               ifp = NULL;
        if (ifp != NULL && !IN6_IS_ADDR_UNSPECIFIED(&pktinfo->ipi6_addr)) {
                ia.s_addr = pktinfo->ipi6_addr.s6_addr32[3];
                if (in_ifhasaddr(ifp, ia) == 0)
diff --git a/sys/netinet6/in6_mcast.c b/sys/netinet6/in6_mcast.c
index 7326befc6d01..b1b161ace1b8 100644
--- a/sys/netinet6/in6_mcast.c
+++ b/sys/netinet6/in6_mcast.c
@@ -1402,6 +1402,7 @@ static int
 in6p_block_unblock_source(struct inpcb *inp, struct sockopt *sopt)
 {
        struct group_source_req          gsr;
+       struct epoch_tracker             et;
        sockunion_t                     *gsa, *ssa;
        struct ifnet                    *ifp;
        struct in6_mfilter              *imf;
@@ -1439,10 +1440,16 @@ in6p_block_unblock_source(struct inpcb *inp, struct 
sockopt *sopt)
                    ssa->sin6.sin6_len != sizeof(struct sockaddr_in6))
                        return (EINVAL);
 
-               if (gsr.gsr_interface == 0 || V_if_index < gsr.gsr_interface)
-                       return (EADDRNOTAVAIL);
-
+               /*
+                * XXXGL: this function should use ifnet_byindex_ref, or
+                * expand the epoch section all the way to where we put
+                * the reference.
+                */
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(gsr.gsr_interface);
+               NET_EPOCH_EXIT(et);
+               if (ifp == NULL)
+                       return (EADDRNOTAVAIL);
 
                if (sopt->sopt_name == MCAST_BLOCK_SOURCE)
                        doblock = 1;
@@ -1629,6 +1636,7 @@ ip6_freemoptions(struct ip6_moptions *imo)
 static int
 in6p_get_source_filters(struct inpcb *inp, struct sockopt *sopt)
 {
+       struct epoch_tracker     et;
        struct __msfilterreq     msfr;
        sockunion_t             *gsa;
        struct ifnet            *ifp;
@@ -1662,9 +1670,13 @@ in6p_get_source_filters(struct inpcb *inp, struct 
sockopt *sopt)
        if (!IN6_IS_ADDR_MULTICAST(&gsa->sin6.sin6_addr))
                return (EINVAL);
 
-       if (msfr.msfr_ifindex == 0 || V_if_index < msfr.msfr_ifindex)
-               return (EADDRNOTAVAIL);
+       /*
+        * XXXGL: this function should use ifnet_byindex_ref, or expand the
+        * epoch section all the way to where the interface is referenced.
+        */
+       NET_EPOCH_ENTER(et);
        ifp = ifnet_byindex(msfr.msfr_ifindex);
+       NET_EPOCH_EXIT(et);
        if (ifp == NULL)
                return (EADDRNOTAVAIL);
        (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);
@@ -1858,12 +1870,16 @@ in6p_lookup_mcast_ifp(const struct inpcb *inp, const 
struct sockaddr_in6 *gsin6)
  *
  * FIXME: The KAME use of the unspecified address (::)
  * to join *all* multicast groups is currently unsupported.
+ *
+ * XXXGL: this function multiple times uses ifnet_byindex() without
+ * proper protection - staying in epoch, or putting reference on ifnet.
  */
 static int
 in6p_join_group(struct inpcb *inp, struct sockopt *sopt)
 {
        struct in6_multi_head            inmh;
        struct group_source_req          gsr;
+       struct epoch_tracker             et;
        sockunion_t                     *gsa, *ssa;
        struct ifnet                    *ifp;
        struct in6_mfilter              *imf;
@@ -1905,9 +1921,11 @@ in6p_join_group(struct inpcb *inp, struct sockopt *sopt)
                if (mreq.ipv6mr_interface == 0) {
                        ifp = in6p_lookup_mcast_ifp(inp, &gsa->sin6);
                } else {
-                       if (V_if_index < mreq.ipv6mr_interface)
-                               return (EADDRNOTAVAIL);
+                       NET_EPOCH_ENTER(et);
                        ifp = ifnet_byindex(mreq.ipv6mr_interface);
+                       NET_EPOCH_EXIT(et);
+                       if (ifp == NULL)
+                               return (EADDRNOTAVAIL);
                }
                CTR3(KTR_MLD, "%s: ipv6mr_interface = %d, ifp = %p",
                    __func__, mreq.ipv6mr_interface, ifp);
@@ -1946,10 +1964,11 @@ in6p_join_group(struct inpcb *inp, struct sockopt *sopt)
                        ssa->sin6.sin6_port = 0;
                        ssa->sin6.sin6_scope_id = 0;
                }
-
-               if (gsr.gsr_interface == 0 || V_if_index < gsr.gsr_interface)
-                       return (EADDRNOTAVAIL);
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(gsr.gsr_interface);
+               NET_EPOCH_EXIT(et);
+               if (ifp == NULL)
+                       return (EADDRNOTAVAIL);
                break;
 
        default:
@@ -2168,6 +2187,7 @@ in6p_leave_group(struct inpcb *inp, struct sockopt *sopt)
 {
        struct ipv6_mreq                 mreq;
        struct group_source_req          gsr;
+       struct epoch_tracker             et;
        sockunion_t                     *gsa, *ssa;
        struct ifnet                    *ifp;
        struct in6_mfilter              *imf;
@@ -2266,9 +2286,9 @@ in6p_leave_group(struct inpcb *inp, struct sockopt *sopt)
         * XXX SCOPE6 lock potentially taken here.
         */
        if (ifindex != 0) {
-               if (V_if_index < ifindex)
-                       return (EADDRNOTAVAIL);
+               NET_EPOCH_ENTER(et);
                ifp = ifnet_byindex(ifindex);
+               NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifp */
                if (ifp == NULL)
                        return (EADDRNOTAVAIL);
                (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);
@@ -2293,7 +2313,9 @@ in6p_leave_group(struct inpcb *inp, struct sockopt *sopt)
                            ip6_sprintf(ip6tbuf, &gsa->sin6.sin6_addr));
                        ifp = in6p_lookup_mcast_ifp(inp, &gsa->sin6);
                } else {
+                       NET_EPOCH_ENTER(et);
                        ifp = ifnet_byindex(ifindex);
+                       NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifp */
                }
                if (ifp == NULL)
                        return (EADDRNOTAVAIL);
@@ -2410,6 +2432,7 @@ out_in6p_locked:
 static int
 in6p_set_multicast_if(struct inpcb *inp, struct sockopt *sopt)
 {
+       struct epoch_tracker     et;
        struct ifnet            *ifp;
        struct ip6_moptions     *imo;
        u_int                    ifindex;
@@ -2421,19 +2444,19 @@ in6p_set_multicast_if(struct inpcb *inp, struct sockopt 
*sopt)
        error = sooptcopyin(sopt, &ifindex, sizeof(u_int), sizeof(u_int));
        if (error)
                return (error);
-       if (V_if_index < ifindex)
-               return (EINVAL);
+       NET_EPOCH_ENTER(et);
        if (ifindex == 0)
                ifp = NULL;
        else {
                ifp = ifnet_byindex(ifindex);
-               if (ifp == NULL)
-                       return (EINVAL);
-               if ((ifp->if_flags & IFF_MULTICAST) == 0)
+               if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
+                       NET_EPOCH_EXIT(et);
                        return (EADDRNOTAVAIL);
+               }
        }
        imo = in6p_findmoptions(inp);
-       imo->im6o_multicast_ifp = ifp;
+       imo->im6o_multicast_ifp = ifp;  /* XXXGL: reference?! */
+       NET_EPOCH_EXIT(et);
        INP_WUNLOCK(inp);
 
        return (0);
@@ -2442,12 +2465,13 @@ in6p_set_multicast_if(struct inpcb *inp, struct sockopt 
*sopt)
 /*
  * Atomically set source filters on a socket for an IPv6 multicast group.
  *
- * SMPng: NOTE: Potentially calls malloc(M_WAITOK) with Giant held.
+ * XXXGL: unsafely exits epoch with ifnet pointer
  */
 static int
 in6p_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
 {
        struct __msfilterreq     msfr;
+       struct epoch_tracker     et;
        sockunion_t             *gsa;
        struct ifnet            *ifp;
        struct in6_mfilter      *imf;
@@ -2477,9 +2501,9 @@ in6p_set_source_filters(struct inpcb *inp, struct sockopt 
*sopt)
 
        gsa->sin6.sin6_port = 0;        /* ignore port */
 
-       if (msfr.msfr_ifindex == 0 || V_if_index < msfr.msfr_ifindex)
-               return (EADDRNOTAVAIL);
+       NET_EPOCH_ENTER(et);
        ifp = ifnet_byindex(msfr.msfr_ifindex);
+       NET_EPOCH_EXIT(et);
        if (ifp == NULL)
                return (EADDRNOTAVAIL);
        (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);
@@ -2758,13 +2782,6 @@ sysctl_ip6_mcast_filters(SYSCTL_HANDLER_ARGS)
        if (namelen != 5)
                return (EINVAL);
 
-       ifindex = name[0];
-       if (ifindex <= 0 || ifindex > V_if_index) {
-               CTR2(KTR_MLD, "%s: ifindex %u out of range",
-                   __func__, ifindex);
-               return (ENOENT);
-       }
-
        memcpy(&mcaddr, &name[1], sizeof(struct in6_addr));
        if (!IN6_IS_ADDR_MULTICAST(&mcaddr)) {
                CTR2(KTR_MLD, "%s: group %s is not multicast",
@@ -2772,6 +2789,7 @@ sysctl_ip6_mcast_filters(SYSCTL_HANDLER_ARGS)
                return (EINVAL);
        }
 
+       ifindex = name[0];
        NET_EPOCH_ENTER(et);
        ifp = ifnet_byindex(ifindex);
        if (ifp == NULL) {
diff --git a/sys/netinet6/ip6_mroute.c b/sys/netinet6/ip6_mroute.c
index 087e0c5059fd..05324dfb94bf 100644
--- a/sys/netinet6/ip6_mroute.c
+++ b/sys/netinet6/ip6_mroute.c
@@ -677,6 +677,7 @@ static struct sockaddr_in6 sin6 = { sizeof(sin6), AF_INET6 
};
 static int
 add_m6if(struct mif6ctl *mifcp)
 {
+       struct epoch_tracker et;
        struct mif6 *mifp;
        struct ifnet *ifp;
        int error;
@@ -692,12 +693,14 @@ add_m6if(struct mif6ctl *mifcp)
                MIF6_UNLOCK();
                return (EADDRINUSE); /* XXX: is it appropriate? */
        }
-       if (mifcp->mif6c_pifi == 0 || mifcp->mif6c_pifi > V_if_index) {
+
+       NET_EPOCH_ENTER(et);
+       if ((ifp = ifnet_byindex(mifcp->mif6c_pifi)) == NULL) {
+               NET_EPOCH_EXIT(et);
                MIF6_UNLOCK();
                return (ENXIO);
        }
-
-       ifp = ifnet_byindex(mifcp->mif6c_pifi);
+       NET_EPOCH_EXIT(et);     /* XXXGL: unsafe ifp */
 
        if (mifcp->mif6c_flags & MIFF_REGISTER) {
                if (reg_mif_num == (mifi_t)-1) {
diff --git a/sys/netinet6/ip6_output.c b/sys/netinet6/ip6_output.c
index 6091951e2ba2..7d8793b691b4 100644
--- a/sys/netinet6/ip6_output.c
+++ b/sys/netinet6/ip6_output.c
@@ -2819,8 +2819,8 @@ ip6_setpktopts(struct mbuf *control, struct ip6_pktopts 
*opt,
                return (EINVAL);
 
        /*
-        * ip6_setpktopt can call ifnet_by_index(), so it's imperative that we 
are
-        * in the net epoch here.
+        * ip6_setpktopt can call ifnet_byindex(), so it's imperative that we
+        * are in the network epoch here.
         */
        NET_EPOCH_ASSERT();
 
@@ -2959,8 +2959,6 @@ ip6_setpktopt(int optname, u_char *buf, int len, struct 
ip6_pktopts *opt,
                if (IN6_IS_ADDR_MULTICAST(&pktinfo->ipi6_addr))
                        return (EINVAL);
                /* validate the interface index if specified. */
-               if (pktinfo->ipi6_ifindex > V_if_index)
-                        return (ENXIO);
                if (pktinfo->ipi6_ifindex) {
                        ifp = ifnet_byindex(pktinfo->ipi6_ifindex);
                        if (ifp == NULL)
diff --git a/sys/netinet6/mld6.c b/sys/netinet6/mld6.c
index c4948158bba8..1f79ef39e40e 100644
--- a/sys/netinet6/mld6.c
+++ b/sys/netinet6/mld6.c
@@ -356,13 +356,13 @@ out_locked:
  * Expose struct mld_ifsoftc to userland, keyed by ifindex.
  * For use by ifmcstat(8).
  *
- * SMPng: NOTE: Does an unlocked ifindex space read.
  * VIMAGE: Assume curvnet set by caller. The node handler itself
  * is not directly virtualized.
  */
 static int
 sysctl_mld_ifinfo(SYSCTL_HANDLER_ARGS)
 {
+       struct epoch_tracker     et;
        int                     *name;
        int                      error;
        u_int                    namelen;
@@ -385,14 +385,9 @@ sysctl_mld_ifinfo(SYSCTL_HANDLER_ARGS)
        IN6_MULTI_LOCK();
        IN6_MULTI_LIST_LOCK();
        MLD_LOCK();
-
-       if (name[0] <= 0 || name[0] > V_if_index) {
-               error = ENOENT;
-               goto out_locked;
-       }
+       NET_EPOCH_ENTER(et);
 
        error = ENOENT;
-
        ifp = ifnet_byindex(name[0]);
        if (ifp == NULL)
                goto out_locked;
@@ -415,6 +410,7 @@ sysctl_mld_ifinfo(SYSCTL_HANDLER_ARGS)
        }
 
 out_locked:
+       NET_EPOCH_EXIT(et);
        MLD_UNLOCK();
        IN6_MULTI_LIST_UNLOCK();
        IN6_MULTI_UNLOCK();
diff --git a/sys/netinet6/nd6_rtr.c b/sys/netinet6/nd6_rtr.c
index cec9fccd63c4..07a4c2cbe7e5 100644
--- a/sys/netinet6/nd6_rtr.c
+++ b/sys/netinet6/nd6_rtr.c
@@ -2425,18 +2425,21 @@ rt6_flush(struct in6_addr *gateway, struct ifnet *ifp)
 int
 nd6_setdefaultiface(int ifindex)
 {
-       int error = 0;
-
-       if (ifindex < 0 || V_if_index < ifindex)
-               return (EINVAL);
-       if (ifindex != 0 && !ifnet_byindex(ifindex))
-               return (EINVAL);
 
        if (V_nd6_defifindex != ifindex) {
                V_nd6_defifindex = ifindex;
-               if (V_nd6_defifindex > 0)
+               if (V_nd6_defifindex != 0) {
+                       struct epoch_tracker et;
+
+                       /*
+                        * XXXGL: this function should use ifnet_byindex_ref!
+                        */
+                       NET_EPOCH_ENTER(et);
                        V_nd6_defifp = ifnet_byindex(V_nd6_defifindex);
-               else
+                       NET_EPOCH_EXIT(et);
+                       if (V_nd6_defifp == NULL)
+                               return (EINVAL);
+               } else
                        V_nd6_defifp = NULL;
 
                /*
@@ -2447,7 +2450,7 @@ nd6_setdefaultiface(int ifindex)
                scope6_setdefault(V_nd6_defifp);
        }
 
-       return (error);
+       return (0);
 }
 
 bool
diff --git a/sys/netinet6/scope6.c b/sys/netinet6/scope6.c
index 099f8a78e14d..7957cec44f79 100644
--- a/sys/netinet6/scope6.c
+++ b/sys/netinet6/scope6.c
@@ -177,16 +177,22 @@ scope6_set(struct ifnet *ifp, struct scope6_id *idlist)
                                return (EINVAL);
                        }
 
-                       if (i == IPV6_ADDR_SCOPE_LINKLOCAL &&
-                           idlist->s6id_list[i] > V_if_index) {
-                               /*
-                                * XXX: theoretically, there should be no
-                                * relationship between link IDs and interface
-                                * IDs, but we check the consistency for
-                                * safety in later use.
-                                */
-                               IF_AFDATA_WUNLOCK(ifp);
-                               return (EINVAL);
+                       if (i == IPV6_ADDR_SCOPE_LINKLOCAL) {
+                               struct epoch_tracker et;
+
+                               NET_EPOCH_ENTER(et);
+                               if (!ifnet_byindex(idlist->s6id_list[i])) {
+                                       /*
+                                        * XXX: theoretically, there should be
+                                        * no relationship between link IDs and
+                                        * interface IDs, but we check the
+                                        * consistency for safety in later use.
+                                        */
+                                       NET_EPOCH_EXIT(et);
+                                       IF_AFDATA_WUNLOCK(ifp);
+                                       return (EINVAL);
+                               }
+                               NET_EPOCH_EXIT(et);
                        }
 
                        /*
@@ -325,14 +331,20 @@ sa6_embedscope(struct sockaddr_in6 *sin6, int defaultok)
        if (zoneid != 0 &&
            (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr) ||
            IN6_IS_ADDR_MC_INTFACELOCAL(&sin6->sin6_addr))) {
+               struct epoch_tracker et;
+
                /*
                 * At this moment, we only check interface-local and
                 * link-local scope IDs, and use interface indices as the
                 * zone IDs assuming a one-to-one mapping between interfaces
                 * and links.
                 */
-               if (V_if_index < zoneid || ifnet_byindex(zoneid) == NULL)
+               NET_EPOCH_ENTER(et);
+               if (ifnet_byindex(zoneid) == NULL) {
+                       NET_EPOCH_EXIT(et);
                        return (ENXIO);
+               }
+               NET_EPOCH_EXIT(et);
 
                /* XXX assignment to 16bit from 32bit variable */
                sin6->sin6_addr.s6_addr16[1] = htons(zoneid & 0xffff);
@@ -358,14 +370,15 @@ sa6_recoverscope(struct sockaddr_in6 *sin6)
                 */
                zoneid = ntohs(sin6->sin6_addr.s6_addr16[1]);
                if (zoneid) {
+                       struct epoch_tracker et;
+
+                       NET_EPOCH_ENTER(et);
                        /* sanity check */
-                       if (V_if_index < zoneid)
-                               return (ENXIO);
-#if 0
-                       /* XXX: Disabled due to possible deadlock. */
-                       if (!ifnet_byindex(zoneid))
+                       if (!ifnet_byindex(zoneid)) {
+                               NET_EPOCH_EXIT(et);
                                return (ENXIO);
-#endif
+                       }
+                       NET_EPOCH_EXIT(et);
                        if (sin6->sin6_scope_id != 0 &&
                            zoneid != sin6->sin6_scope_id) {
                                log(LOG_NOTICE,

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