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sonic-net / sonic-buildimage

Scripts which perform an installable binary image build for SONiC
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ICMPv6 type2 (A Packet Too Big) is not sent by SONiC switch in response to a packet that it cannot forward because the packet is larger than the MTU of the outgoing link. #4479

Open madhanmellanox opened 4 years ago

madhanmellanox commented 4 years ago

Description

Steps to reproduce the issue:

  1. configure switch with an ingress VLAN interface and egress VLAN interface with ipv6 address of different subnets respectively. Configure MTU of egress VLAN interface to say, 1500.
  2. Attach Traffic generator ports to both ingress port and egress port of the switch. Send end-end-end ipv6 traffic of size say, 2000.
  3. Run tcpdump over source VLAN interface and expecting "ICMPv6 type 2 Packet Too Big" messages to be seen. But, the ICMPv6 message won't be received by the tcpdump..

Describe the results you received: I did not receive ICMPv6 type 2 Packet Too Big error messages to be sent towards the source of the end-to-end ipv6 traffic.

Describe the results you expected: I expected to receive ICMPv6 type 2 Packet Too Big error messages to be sent towards the source of the end-to-end ipv6 traffic.

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

```

show ver

SONiC Software Version: SONiC.master.0-dirty-20200114.131506 Distribution: Debian 9.11 Kernel: 4.9.0-9-2-amd64 Build commit: 952dfb15 Build date: Tue Jan 14 13:28:50 UTC 2020 Built by: volodymyrs@r-build-sonic03

Platform: x86_64-mlnx_msn2100-r0 HwSKU: ACS-MSN2100 ASIC: mellanox Serial Number: MT1646X05314 Uptime: 18:29:24 up 3:16, 1 user, load average: 3.33, 3.24, 3.25

Docker images: REPOSITORY TAG IMAGE ID SIZE docker-platform-monitor latest aabdbf5b55b9 569MB docker-platform-monitor master.0-dirty-20200114.131506 aabdbf5b55b9 569MB docker-sflow latest acc6d9a905f3 306MB docker-sflow master.0-dirty-20200114.131506 acc6d9a905f3 306MB docker-fpm-frr latest 2e17fdf8f565 325MB docker-fpm-frr master.0-dirty-20200114.131506 2e17fdf8f565 325MB docker-syncd-mlnx latest 09df8b1f23d7 377MB docker-syncd-mlnx master.0-dirty-20200114.131506 09df8b1f23d7 377MB docker-orchagent latest 6729c2e779af 323MB docker-orchagent master.0-dirty-20200114.131506 6729c2e779af 323MB docker-teamd latest a710f94fa26c 305MB docker-teamd master.0-dirty-20200114.131506 a710f94fa26c 305MB docker-snmp-sv2 latest e4c726145422 339MB docker-snmp-sv2 master.0-dirty-20200114.131506 e4c726145422 339MB docker-lldp-sv2 latest d67cfab77277 303MB docker-lldp-sv2 master.0-dirty-20200114.131506 d67cfab77277 303MB docker-sonic-mgmt-framework latest 544660d56163 330MB docker-sonic-mgmt-framework master.0-dirty-20200114.131506 544660d56163 330MB docker-sonic-telemetry latest 7df4698f004b 343MB docker-sonic-telemetry master.0-dirty-20200114.131506 7df4698f004b 343MB docker-sonic-restapi latest 6834d43af7fb 293MB docker-sonic-restapi master.0-dirty-20200114.131506 6834d43af7fb 293MB docker-router-advertiser latest 2fa815e41d75 282MB docker-router-advertiser master.0-dirty-20200114.131506 2fa815e41d75 282MB docker-database latest 681324505d5c 282MB docker-database master.0-dirty-20200114.131506 681324505d5c 282MB docker-dhcp-relay latest a3dfa0aa88e9 292MB docker-dhcp-relay master.0-dirty-20200114.131506 a3dfa0aa88e9 292MB sonic_dump_r-ethernet-sw230_20200123_164107 (1).tar.gz

```

**Attach debug file `sudo generate_dump`:**

```
(paste your output here)
```
xinliu-seattle commented 4 years ago

Volod will help to get more input.

xinliu-seattle commented 4 years ago

Debian 4.19 might have this fixed.

madhanmellanox commented 4 years ago

The issue is not fixed with Debian 4.19. We are not receiving ICMPv6 Destination Unreachable - Packet Too Big messages towards the source. The issue is not only seen with outgoing SVI IPv6 interface. The issue is seen with any outgoing routed IPv6 interface also.