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ISIS invalid format of hello packet when interface mtu is between 1501 and 1535 #14924

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aapostoliuk opened this issue Dec 1, 2023 · 7 comments
Closed
2 tasks done

ISIS invalid format of hello packet when interface mtu is between 1501 and 1535 #14924

aapostoliuk opened this issue Dec 1, 2023 · 7 comments
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triage Needs further investigation

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@aapostoliuk
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Describe the bug
FRR creates an invalid format of the hello ISIS packet when interface MTU is between 1501 and 1535.
The lab:
Cisco Router <---> FRR directly connected.
MTU is set to 1508

Configurations:
FRR configuration:

debian# show run
Building configuration...

Current configuration:
!
frr version 9.2-dev-MyOwnFRRVersion
frr defaults traditional
hostname debian
service integrated-vtysh-config
!
interface ens36
 ip router isis test
exit
!
router isis test
 net 49.0001.0000.0000.0001.00
exit
!
end
debian#

Interface configuration:

root@debian:~# ip addr show dev ens36
3: ens36: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1508 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:65:cf:87 brd ff:ff:ff:ff:ff:ff
    altname enp2s4
    inet 192.168.100.5/24 brd 192.168.100.255 scope global ens36
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe65:cf87/64 scope link proto kernel_ll
       valid_lft forever preferred_lft forever
root@debian:~# ip link show ens36
3: ens36: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1508 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:65:cf:87 brd ff:ff:ff:ff:ff:ff
    altname enp2s4

Cisco configuration:

interface GigabitEthernet0/0
 mtu 1508
 ip address 192.168.100.110 255.255.255.0
 ip router isis
 duplex auto
 speed auto
 media-type rj45

router isis
 net 49.0001.0000.0000.0004.00

ISIS neighbors status
FRR output:

debian# show isis neighbor
Area test:
  System Id           Interface   L  State        Holdtime SNPA
 Router              ens36       1  Initializing  24       000c.2989.2dd6
 Router              ens36       2  Initializing  28       000c.2989.2dd6

Cisco output:

Router#show isis neighbors

System Id      Type Interface   IP Address      State Holdtime Circuit Id

Debugging:
FRR side:

debian# debug isis adj-packets
IS-IS Adjacency related packets debugging is on
debian# terminal monitor
2023-12-01 11:04:22.874 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L1 LAN IIH on ens36, length 1505
2023-12-01 11:04:23.394 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L2 LAN IIH on ens36, length 1505
2023-12-01 11:04:24.248 [DEBG] isisd: [H3GFN-BXSRF] ISIS-Adj (test): Rcvd L1 LAN IIH on ens36, cirType L1L2, cirID 3
2023-12-01 11:04:24.248 [DEBG] isisd: [SCM84-DFK6R] ISIS-Adj (test): Rcvd L1 LAN IIH from 000c.2989.2dd6 on ens36, cirType L1L2, cirID 3, length 1505
2023-12-01 11:04:25.739 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L1 LAN IIH on ens36, length 1505
2023-12-01 11:04:26.155 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L2 LAN IIH on ens36, length 1505
2023-12-01 11:04:26.393 [DEBG] isisd: [H3GFN-BXSRF] ISIS-Adj (test): Rcvd L2 LAN IIH on ens36, cirType L1L2, cirID 3
2023-12-01 11:04:26.393 [DEBG] isisd: [SCM84-DFK6R] ISIS-Adj (test): Rcvd L2 LAN IIH from 000c.2989.2dd6 on ens36, cirType L1L2, cirID 3, length 1505
2023-12-01 11:04:28.702 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L1 LAN IIH on ens36, length 1505
2023-12-01 11:04:29.052 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L2 LAN IIH on ens36, length 1505
2023-12-01 11:04:31.514 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L1 LAN IIH on ens36, length 1505
2023-12-01 11:04:31.760 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L2 LAN IIH on ens36, length 1505
2023-12-01 11:04:32.988 [DEBG] isisd: [H3GFN-BXSRF] ISIS-Adj (test): Rcvd L1 LAN IIH on ens36, cirType L1L2, cirID 3
2023-12-01 11:04:32.988 [DEBG] isisd: [SCM84-DFK6R] ISIS-Adj (test): Rcvd L1 LAN IIH from 000c.2989.2dd6 on ens36, cirType L1L2, cirID 3, length 1505
2023-12-01 11:04:34.488 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L1 LAN IIH on ens36, length 1505
2023-12-01 11:04:34.632 [DEBG] isisd: [SKACH-0THYP] ISIS-Adj (test): Sending L2 LAN IIH on ens36, length 1505

Cisco side:

Router#debug isis adj-packets
IS-IS Adjacency related packets debugging is on for router process null
Router#
*Dec  1 11:05:42.898: ISIS-Adj: Sending L1 LAN IIH on GigabitEthernet0/0, length 1505
*Dec  1 11:05:46.646: ISIS-Adj: Sending L2 LAN IIH on GigabitEthernet0/0, length 1505
*Dec  1 11:05:51.022: ISIS-Adj: Sending L1 LAN IIH on GigabitEthernet0/0, length 1505
*Dec  1 11:05:56.108: ISIS-Adj: Sending L2 LAN IIH on GigabitEthernet0/0, length 1505

Tcpdump on FRR side:

root@debian:~# tcpdump -i ens36
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on ens36, link-type EN10MB (Ethernet), snapshot length 262144 bytes
11:07:07.747223 00:0c:29:65:cf:87 (oui Unknown) > 01:80:c2:00:00:14 (oui Unknown), ethertype Unknown (0x05e4), length 1522:
        0x0000:  fefe 0383 1b01 000f 0100 0003 0000 0000  ................
        0x0010:  0001 001e 05e1 4000 0000 0000 0401 8101  ......@.........
        0x0020:  cc01 0403 4900 0106 0600 0c29 892d d684  ....I......).-..
        0x0030:  04c0 a864 0508 ff00 0000 0000 0000 0000  ...d............
        0x0040:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0050:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0060:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0070:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0080:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0090:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x00a0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x00b0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x00c0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x00d0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x00e0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x00f0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0100:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0110:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0120:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0130:  0000 0000 0000 08ff 0000 0000 0000 0000  ................
        0x0140:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0150:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0160:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0170:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0180:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0190:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x01a0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x01b0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x01c0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x01d0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x01e0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x01f0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0200:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0210:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0220:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0230:  0000 0000 0000 0008 ff00 0000 0000 0000  ................
        0x0240:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0250:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0260:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0270:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0280:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0290:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x02a0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x02b0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x02c0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x02d0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x02e0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x02f0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0300:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0310:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0320:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0330:  0000 0000 0000 0000 08ff 0000 0000 0000  ................
        0x0340:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0350:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0360:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0370:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0380:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0390:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x03a0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x03b0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x03c0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x03d0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x03e0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x03f0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0400:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0410:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0420:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0430:  0000 0000 0000 0000 0008 ff00 0000 0000  ................
        0x0440:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0450:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0460:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0470:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0480:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0490:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x04a0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x04b0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x04c0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x04d0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x04e0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x04f0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0500:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0510:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0520:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0530:  0000 0000 0000 0000 0000 08a8 0000 0000  ................
        0x0540:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0550:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0560:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0570:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0580:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x0590:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x05a0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x05b0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x05c0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x05d0:  0000 0000 0000 0000 0000 0000 0000 0000  ................
        0x05e0:  0000 0000                                ....
11:07:07.856228 IS-IS, L2 Lan IIH, src-id 0000.0000.0004, lan-id 0000.0000.0004.01, prio 64, length 1505

Cisco does not understand this packet.
If we set MTU 1500 or 1536 on both sides, everything works.
But if we create the lab FRR<-->FRR, routers will understand this packet as hello and adjacency will created.

  • Did you check if this is a duplicate issue?
  • Did you test it on the latest FRRouting/frr master branch?

Versions

  • OS Version: Debian GNU/Linux trixie/sid
  • Kernel: 6.1.0-7-amd64
  • FRR Version: frr-9.2-dev-136-ge6e846de2

I have tested it on Debian 12 the result was the same.
@aapostoliuk aapostoliuk added the triage Needs further investigation label Dec 1, 2023
@donaldsharp
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can you give us a pcap of the packets being generated from FRR?

@aapostoliuk
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isis1508.dmp
tcpdump -i ens36 ether host 00:0c:29:65:cf:87 -s 65535 -w isis1508.dmp

@odd22
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odd22 commented Jan 23, 2024

Capture is strange. When I open it into wireshark I got Invalid Length/Type error for the Ethernet frames. Only source and destination mac addresses are recognized.

@aapostoliuk
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Yes. I see the same in Wireshark.

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This issue is stale because it has been open 180 days with no activity. Comment or remove the autoclose label in order to avoid having this issue closed.

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frrbot bot commented Jul 23, 2024

This issue will be automatically closed in the specified period unless there is further activity.

@frrbot frrbot bot closed this as completed Jul 30, 2024
@frrbot frrbot bot removed the autoclose label Jul 30, 2024
@dmbaturin
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The issue may have no activity, but was it fixed?

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@dmbaturin @odd22 @donaldsharp @aapostoliuk