Is it platform specific
generic
Importance or Severity
Critical
Description of the bug
On the SONiC VPP platform, packets with an IPv4 destination in 240.0.0.0/4 (and 224.0.0.0/4) are silently dropped inside ip4-lookup even when SONiC has installed a route covering them (e.g. the default route). Other ASIC platforms (BCM, MLNX) do not impose this filter, so the same SONiC route table behaves differently on VPP.
Concretely this breaks test_decap, whose IPIP inner destinations land in 240.0.0.0/4.
Upstream VPP installs a fixed set of high-priority drop entries into every IPv4 FIB at table creation:
https://github.com/FDio/vpp/blob/2044332c908702fbe2ca7b370f75dbd7c2ae6dad/src/vnet/fib/ip4_fib.c#L13-L90
| prefix |
source |
overridable? |
| 0.0.0.0/0 |
FIB_SOURCE_DEFAULT_ROUTE |
yes |
| 0.0.0.0/32 |
FIB_SOURCE_DEFAULT_ROUTE |
yes |
| 224.0.0.0/4 |
FIB_SOURCE_SPECIAL |
no |
| 240.0.0.0/4 |
FIB_SOURCE_SPECIAL |
no |
| 255.255.255.255/32 |
FIB_SOURCE_DEFAULT_ROUTE |
yes |
Steps to Reproduce
vpp# show ip fib 240.0.0.0
ipv4-VRF:0, fib_index:0, flow hash:[src dst sport dport proto ] epoch:0 flags:none locks:[adjacency:1, recursive-resolution:8, default-route:1, ]
240.0.0.0/4 fib:0 index:2 locks:2
special refs:1 entry-flags:drop, src-flags:added,contributing,active,
path-list:[2] locks:2 flags:drop, uPRF-list:2 len:0 itfs:[]
path:[2] pl-index:2 ip4 weight=1 pref=0 special: cfg-flags:drop,
[@0]: dpo-drop ip4
forwarding: unicast-ip4-chain
[@0]: dpo-load-balance: [proto:ip4 index:3 buckets:1 uRPF:2 to:[40037:4003700]]
[0] [@0]: dpo-drop ip4
Actual Behavior and Expected Behavior
the route in the VPP should be the same as the bgp fib:
root@vlab-vpp-02:~# show ip route 240.0.0.0
Routing entry for 0.0.0.0/0
Known via "bgp", distance 20, metric 0, best
Last update 02:39:22 ago
* 10.0.0.57, via PortChannel101
* 10.0.0.59, via PortChannel102
* 10.0.0.61, via PortChannel103
* 10.0.0.63, via PortChannel104
Relevant log output
Output of show version, show techsupport
Attach files (if any)
No response
Is it platform specific
generic
Importance or Severity
Critical
Description of the bug
On the SONiC VPP platform, packets with an IPv4 destination in 240.0.0.0/4 (and 224.0.0.0/4) are silently dropped inside ip4-lookup even when SONiC has installed a route covering them (e.g. the default route). Other ASIC platforms (BCM, MLNX) do not impose this filter, so the same SONiC route table behaves differently on VPP.
Concretely this breaks test_decap, whose IPIP inner destinations land in 240.0.0.0/4.
Upstream VPP installs a fixed set of high-priority drop entries into every IPv4 FIB at table creation:
https://github.com/FDio/vpp/blob/2044332c908702fbe2ca7b370f75dbd7c2ae6dad/src/vnet/fib/ip4_fib.c#L13-L90
Steps to Reproduce
Actual Behavior and Expected Behavior
the route in the VPP should be the same as the bgp fib:
Relevant log output
Output of
show version,show techsupportAttach files (if any)
No response