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zebra: fix handle netlink state reachable message
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When creating an NHRP shortcut entry between two spokes, the cache
entry created has very often a field 'used' set to false, despite
a continuous traffic towards the 11.255.255.1 IP address.

> north-vm# show ip nhrp cache
> Iface    Type     Protocol                 NBMA                     Claimed NBMA             Flags  Identity
> gre1     local    11.255.255.2             10.125.0.2               10.125.0.2                      -
> gre1     nhs      11.255.255.1             10.125.0.1               10.125.0.1               T     west     <----

Actually, that flag reflects the protocol address reachability. A neighbor
entry is maintained in the kernel. As an ARP probe operates only with MAC
address, NHRP will take the place of ARP, and will refresh the NBMA link IP
address, every time the neighbor entry enters in PROBE state. The neighbor
entry state goes in REACHABLE state, and the expectation is that the REACHABLE
state is notified to the NHRP daemon, which does not happen.

The below dump indicates 3 netlink messages over the gre1 interface:

> # trace from 'ip monitor neigh'
> miss 11.255.255.1 dev gre1 lladdr 10.125.0.1 PROBE proto 191
> 11.255.255.1 dev gre1 lladdr 10.125.0.1 PROBE proto 191
> 11.255.255.1 dev gre1 lladdr 10.125.0.1 REACHABLE proto 191

The NHRP/ZEBRA traces indicate the first 2 netlink messages received, followed
by the update of the neighbor entry by the NHRP daemon. But there is no
reception or confirmation that the new neighbor state moved to REACHABLE.

> # trace from nhrp
> 2023/11/06 09:46:21 ZEBRA: [V8KNF-8EXH8] netlink_recv_msg: << netlink message dump [recv]
> 2023/11/06 09:46:21 ZEBRA: [JAS4D-NCWGP] nlmsghdr [len=80 type=(30) GETNEIGH flags=(0x0001) {REQUEST} seq=0 pid=0]
> 2023/11/06 09:46:21 ZEBRA: [S4WS4-PS3KF] netlink_parse_info: netlink-listen (NS 0) type RTM_GETNEIGH(30), len=80, seq=0, pid=0
> 2023/11/06 09:46:21 ZEBRA: [V8KNF-8EXH8] netlink_recv_msg: << netlink message dump [recv]
> 2023/11/06 09:46:21 ZEBRA: [JAS4D-NCWGP] nlmsghdr [len=80 type=(28) NEWNEIGH flags=(0x0000) {} seq=0 pid=0]
> 2023/11/06 09:46:21 ZEBRA: [T4YQJ-83R8H]   ndm [family=2 (AF_INET) ifindex=10 state=0x0010 {PROBE} flags=0x0000 {} type=1 (UNICAST)]
> 2023/11/06 09:46:21 ZEBRA: [KFBSR-XYJV1]     rta [len=8 (payload=4) type=(1) DST]
> 2023/11/06 09:46:21 ZEBRA: [M8QV4-KY9C0]       11.255.255.1
> 2023/11/06 09:46:21 ZEBRA: [KFBSR-XYJV1]     rta [len=8 (payload=4) type=(2) LLADDR]
> 2023/11/06 09:46:21 ZEBRA: [V74GD-NYS6Y]       0A:7D:00:01
> 2023/11/06 09:46:21 ZEBRA: [KFBSR-XYJV1]     rta [len=8 (payload=4) type=(4) PROBES]
> 2023/11/06 09:46:21 ZEBRA: [KFBSR-XYJV1]     rta [len=20 (payload=16) type=(3) CACHEINFO]
> 2023/11/06 09:46:21 ZEBRA: [KFBSR-XYJV1]     rta [len=5 (payload=1) type=(12) UNKNOWN]
> 2023/11/06 09:46:21 ZEBRA: [S4WS4-PS3KF] netlink_parse_info: netlink-listen (NS 0) type RTM_NEWNEIGH(28), len=76, seq=0, pid=0
> 2023/11/06 09:46:21 ZEBRA: [TDS34-MNEJW]     Neighbor Entry received is not on a VLAN or a BRIDGE, ignoring
> 2023/11/06 09:46:21 NHRP: [QQ0NK-1H449] Netlink: who-has 11.255.255.1 dev gre1 lladdr 10.125.0.1 nud 0x10 cache used 0 type 5
> 2023/11/06 09:46:21 NHRP: [QVXNM-NVHEQ] Netlink: update binding for 11.255.255.1 dev gre1 from c (unspec) peer.vc.nbma 10.125.0.1 to lladdr 10.125.0.1
> 2023/11/06 09:46:21 NHRP: [QQ0NK-1H449] Netlink: new-neigh 11.255.255.1 dev gre1 lladdr 10.125.0.1 nud 0x10 cache used 1 type 5
> 2023/11/06 09:46:21 ZEBRA: [NH6N7-54CD1] Tx RTM_NEWNEIGH family ipv4 IF gre1(10) Neigh 11.255.255.1 Link  10.125.0.1 flags 0x0 state 0x2 ext_flags 0x0
> 2023/11/06 09:46:21 ZEBRA: [HYEHE-CQZ9G] nl_batch_send: netlink-dp (NS 0), batch size=52, msg cnt=1

The NHRP daemon uses the ZEBRA netlink layer to update the binding, and uses a
netlink socket for writing, which is different than the netlink socket used for
reading. There is no confirmation that the write operation succeeded when the
ZEBRA daemon is the initiator of the write operation. Previously, the write
and read operations were directly done on a netlink socket from NHRP, and was
working ok.

Fix this by reading the return status of the netlink write operation, and link
it to the neighbor notification message to inform NHRP of the REACHABLE state.

> north-vm# show ip nhrp cache
> Iface    Type     Protocol                 NBMA                     Claimed NBMA             Flags  Identity
> gre1     local    11.255.255.2             10.125.0.2               10.125.0.2                      -
> gre1     nhs      11.255.255.1             10.125.0.1               10.125.0.1               UT     west     <----

Link: https://flylib.com/books/3/475/1/html/2/images/0131777203/graphics/15fig06.gif
Fixes: b3b7510 ("nhrpd: link layer registration to notificationas")
Signed-off-by: Philippe Guibert <[email protected]>
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@pguibert6WIND
pguibert6WIND committed Nov 6, 2023
1 parent 2485aeb commit 9378d4a
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Showing 3 changed files with 44 additions and 1 deletion.
38 changes: 38 additions & 0 deletions zebra/zapi_msg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -998,6 +998,44 @@ void zsend_nhrp_neighbor_notify(int cmd, struct interface *ifp,
}
}

void zsend_nhrp_neighbor_dataplane_notify(const struct zebra_dplane_ctx *ctx)
{
struct interface *ifp;
int ndm_state = 0;
const struct ipaddr *link_addr, *ip_addr;
union sockunion link_layer_ipv4;

if (dplane_ctx_get_status(ctx) != ZEBRA_DPLANE_REQUEST_SUCCESS)
/* failed write operations are not notified */
return;

ifp = if_lookup_by_index(dplane_ctx_get_ifindex(ctx),
dplane_ctx_get_vrf(ctx));
if (!ifp)
return;

link_addr = dplane_ctx_neigh_get_link_ip(ctx);
if (!link_addr || ipaddr_family(link_addr) != IPADDR_V4)
/* non link ipv4 address are not considered */
return;

if (dplane_ctx_neigh_get_state(ctx) == DPLANE_NUD_REACHABLE)
ndm_state = ZEBRA_NEIGH_STATE_REACHABLE;
else if (dplane_ctx_neigh_get_state(ctx) == DPLANE_NUD_FAILED)
ndm_state = ZEBRA_NEIGH_STATE_FAILED;
else
return;

sockunion_family(&link_layer_ipv4) = AF_INET;
memcpy((void *)sockunion_get_addr(&link_layer_ipv4),
&link_addr->ipaddr_v4, 4);

ip_addr = dplane_ctx_neigh_get_ipaddr(ctx);

zsend_nhrp_neighbor_notify(ZEBRA_NHRP_NEIGH_ADDED, ifp,
(struct ipaddr *)ip_addr, ndm_state,
&link_layer_ipv4);
}

/* Router-id is updated. Send ZEBRA_ROUTER_ID_UPDATE to client. */
int zsend_router_id_update(struct zserv *client, afi_t afi, struct prefix *p,
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2 changes: 2 additions & 0 deletions zebra/zapi_msg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,8 @@ extern int zsend_sr_policy_notify_status(uint32_t color,
extern void zsend_nhrp_neighbor_notify(int cmd, struct interface *ifp,
struct ipaddr *ipaddr, int ndm_state,
union sockunion *link_layer_ipv4);
extern void
zsend_nhrp_neighbor_dataplane_notify(const struct zebra_dplane_ctx *ctx);

extern int zsend_client_close_notify(struct zserv *client,
struct zserv *closed_client);
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5 changes: 4 additions & 1 deletion zebra/zebra_rib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4903,13 +4903,16 @@ static void rib_process_dplane_results(struct event *thread)
case DPLANE_OP_TC_FILTER_UPDATE:
break;

case DPLANE_OP_NEIGH_IP_INSTALL:
zsend_nhrp_neighbor_dataplane_notify(ctx);
break;

/* Some op codes not handled here */
case DPLANE_OP_ADDR_INSTALL:
case DPLANE_OP_ADDR_UNINSTALL:
case DPLANE_OP_NEIGH_INSTALL:
case DPLANE_OP_NEIGH_UPDATE:
case DPLANE_OP_NEIGH_DELETE:
case DPLANE_OP_NEIGH_IP_INSTALL:
case DPLANE_OP_NEIGH_IP_DELETE:
case DPLANE_OP_VTEP_ADD:
case DPLANE_OP_VTEP_DELETE:
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