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Forum Topic - DHCP inform not sent: (2 Items)
   
Update
John Efstathiades
05/10/2019 1:37 PM
post119702
DHCP inform not sent   
Hello,

I am having a problem with DHCP on a specific interface. The stack sends out a DHCP Discover message and then receives a
 DHCP Offer from the DHCP server but I don't see a DHCP Request sent out.

If I run DHCP client in foreground with verbose output I see that it does not think the DHCP Offer has been received. I 
have instrumented the network driver and verified the DHCP Offer packet is received and is consistent with the data 
shown in Wireshark. This packet is passed to the stack.

Is there any other stack or DHCP client logging I can use to determine why it is ignoring the DHCP Offer message?

I am using the default QNX 7 SDP DHCP client configuration files.

Thanks,
John
John Efstathiades
05/14/2019 12:14 PM
post119705
Re: DHCP inform not sent   
To answer my own question:

The dhclient use a packet filter to listen to replies from the DHCP server. The network driver must therefore include 
support for packet filtering in the receive path. My driver did not so dhclient was not seeing any messages from the 
DHCP server.

Added the following code:
#if NBPFILTER > 0
            /* Pass this up to any BPF listeners. */
            if (ifp->if_bpf) {
                bpf_mtap(ifp->if_bpf, m);
            }
#endif
to the receive path fixed the problem.

This is mentioned briefly in the chapter Packet Filtering in the Core Networking with io-pkt User's Guide.

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