Skip to content

Commit

Permalink
net, neigh: Enable state migration between NUD_PERMANENT and NTF_USE
Browse files Browse the repository at this point in the history 
[ Upstream commit 3dc20f4 ]

Currently, it is not possible to migrate a neighbor entry between NUD_PERMANENT
state and NTF_USE flag with a dynamic NUD state from a user space control plane.
Similarly, it is not possible to add/remove NTF_EXT_LEARNED flag from an existing
neighbor entry in combination with NTF_USE flag.

This is due to the latter directly calling into neigh_event_send() without any
meta data updates as happening in __neigh_update(). Thus, to enable this use
case, extend the latter with a NEIGH_UPDATE_F_USE flag where we break the
NUD_PERMANENT state in particular so that a latter neigh_event_send() is able
to re-resolve a neighbor entry.

Before fix, NUD_PERMANENT -> NUD_* & NTF_USE:

  # ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
  [...]
  # ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
  [...]

As can be seen, despite the admin-triggered replace, the entry remains in the
NUD_PERMANENT state.

After fix, NUD_PERMANENT -> NUD_* & NTF_USE:

  # ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
  [...]
  # ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn REACHABLE
  [...]
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn STALE
  [...]
  # ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
  [...]

After the fix, the admin-triggered replace switches to a dynamic state from
the NTF_USE flag which triggered a new neighbor resolution. Likewise, we can
transition back from there, if needed, into NUD_PERMANENT.

Similar before/after behavior can be observed for below transitions:

Before fix, NTF_USE -> NTF_USE | NTF_EXT_LEARNED -> NTF_USE:

  # ./ip/ip n replace 192.168.178.30 dev enp5s0 use
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
  [...]
  # ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
  [...]

After fix, NTF_USE -> NTF_USE | NTF_EXT_LEARNED -> NTF_USE:

  # ./ip/ip n replace 192.168.178.30 dev enp5s0 use
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
  [...]
  # ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn REACHABLE
  [...]
  # ./ip/ip n replace 192.168.178.30 dev enp5s0 use
  # ./ip/ip n
  192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
  [..]

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Roopa Prabhu <roopa@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
  • Loading branch information
@borkmann @gregkh
borkmann authored and gregkh committed Nov 18, 2021
1 parent 6a85f01 commit 1f03911
Show file tree
Hide file tree
Showing 2 changed files with 14 additions and 9 deletions.
1 change: 1 addition & 0 deletions include/net/neighbour.h
View file
Expand Up @@ -253,6 +253,7 @@ static inline void *neighbour_priv(const struct neighbour *n)
#define NEIGH_UPDATE_F_OVERRIDE 0x00000001
#define NEIGH_UPDATE_F_WEAK_OVERRIDE 0x00000002
#define NEIGH_UPDATE_F_OVERRIDE_ISROUTER 0x00000004
#define NEIGH_UPDATE_F_USE 0x10000000
#define NEIGH_UPDATE_F_EXT_LEARNED 0x20000000
#define NEIGH_UPDATE_F_ISROUTER 0x40000000
#define NEIGH_UPDATE_F_ADMIN 0x80000000
Expand Down
22 changes: 13 additions & 9 deletions net/core/neighbour.c
View file
Expand Up @@ -1217,7 +1217,7 @@ static void neigh_update_hhs(struct neighbour *neigh)
lladdr instead of overriding it
if it is different.
NEIGH_UPDATE_F_ADMIN means that the change is administrative.
NEIGH_UPDATE_F_USE means that the entry is user triggered.
NEIGH_UPDATE_F_OVERRIDE_ISROUTER allows to override existing
NTF_ROUTER flag.
NEIGH_UPDATE_F_ISROUTER indicates if the neighbour is known as
Expand Down Expand Up @@ -1255,6 +1255,12 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
goto out;

ext_learn_change = neigh_update_ext_learned(neigh, flags, &notify);
if (flags & NEIGH_UPDATE_F_USE) {
new = old & ~NUD_PERMANENT;
neigh->nud_state = new;
err = 0;
goto out;
}

if (!(new & NUD_VALID)) {
neigh_del_timer(neigh);
Expand Down Expand Up @@ -1963,22 +1969,20 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,

if (protocol)
neigh->protocol = protocol;

if (ndm->ndm_flags & NTF_EXT_LEARNED)
flags |= NEIGH_UPDATE_F_EXT_LEARNED;

if (ndm->ndm_flags & NTF_ROUTER)
flags |= NEIGH_UPDATE_F_ISROUTER;
if (ndm->ndm_flags & NTF_USE)
flags |= NEIGH_UPDATE_F_USE;

if (ndm->ndm_flags & NTF_USE) {
err = __neigh_update(neigh, lladdr, ndm->ndm_state, flags,
NETLINK_CB(skb).portid, extack);
if (!err && ndm->ndm_flags & NTF_USE) {
neigh_event_send(neigh, NULL);
err = 0;
} else
err = __neigh_update(neigh, lladdr, ndm->ndm_state, flags,
NETLINK_CB(skb).portid, extack);

}
neigh_release(neigh);

out:
return err;
}
Expand Down

0 comments on commit 1f03911

Please sign in to comment.