bad udp checksums found when sending a DHCPDISCOVER packet to SONiC switch(enable DHCP relay)

[okanchou9]

Hi,

When I configured the DHCP server information on minigraph.xml and setup a DHCP client(ubuntu) to send out the DHCPDISCOVER packet to test the DHCP relay but get bad udp checksums error message in /var/log/syslog:

Sep 4 08:04:56.0 sonic INFO dhcrelay: 7 bad udp checksums in 13 packets

Would like to know is the DHCP relay feature is working now or not.

Sample minigraph.xml(Only DHCP part):

<VlanInterfaces> <VlanInterface> <Name>Vlan1000</Name> <AttachTo>Ethernet0;Ethernet4;Ethernet8;Ethernet12;Ethernet16;Ethernet20;Ethernet24;Ethernet28;Ethernet32;Ethernet36;Ethernet40;Ethernet44;Ethernet48;Ethernet52;Ethernet56;Ethernet60;Ethernet64;Ethernet68;Ethernet72;Ethernet76;Ethernet80;Ethernet84;Ethernet88;Ethernet92;Ethernet96;Ethernet100;Ethernet104;Ethernet108</AttachTo> <NoDhcpRelay>False</NoDhcpRelay> <StaticDHCPRelay>0.0.0.0/0</StaticDHCPRelay> <Type i:nil="true"/> <VlanID>1000</VlanID> <Tag>1000</Tag> <Subnets>192.168.0.0/27</Subnets> </VlanInterface> </VlanInterfaces>

<a:DeviceProperty> <a:Name>DhcpResources</a:Name> <a:Reference i:nil="true"/> <a:Value>10.0.0.1;10.0.0.3;10.0.0.5;10.0.0.7</a:Value> </a:DeviceProperty>

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Regards,
Kenie Liu

[jleveque]

DHCP relay agent should be currently working. A few questions:

• Am I correct to assume the DHCP handshake not completing?
• Have you determined that the packets with bad UDP checksums are the DHCPDISCOVER packets coming from the client or are they DHCPOFFER packets coming back from the server?
• Would it be possible to try a different client?

[okanchou9]

Hi jleveque,

• Am I correct to assume the DHCP handshake not completing?

Kenie: No, I think the DHCP handshaking wasn't executed since SONiC switch recognized this DHCPDISCOVER packet as an illegal packet due to bad UDP checksums. Also I didn't see SONiC switch relay the DHCPDISCOVER packet to DHCP server, too.

• Have you determined that the packets with bad UDP checksums are the DHCPDISCOVER packets coming from the client or are they DHCPOFFER packets coming back from the server?

• Would it be possible to try a different client?

Kenie: Yes, please refer the attachment for the pcap file that I captured on SONiC switch. I tried 3 different devices(a docker PTF provided by sonic-buildimage, an Ubuntu server and a switch) to send out DHCPDISCOVER packet but all got bad udp checksums in syslog. I'm sure all DHCPDISCOVER packets sent from 3 devices are correct without any issue.

Capture.zip

[jleveque]

Hi Kenie,

Could you please run tcpdump simultaneously on both the client and the SONiC switch and capture a DHCPDISCOVER packet being sent? I'd like to compare the packets and their checksums on both devices. Thanks.

[jleveque]

@okanchou9: Since you have not responded in over two years, I am assuming this issue is resolved. Please feel free to reopen the issue if need be.