iPXE Not Making Requests to Port 4011

[cjs]

First, thanks for your help with this issue!

(2017-02-03 23:50)NiKiZe Wrote:  Proxy dhcp can be disabled by the main dhcp server via a option.

Ah. I've looked into this a bit (the Gist you mentioned was very helpful) and, if I'm understanding this right, the primary DHCP server can send back a reply with DHCP option 175 set to say "don't attempt to contact a proxy server," right? (I'm not sure what the ipxe-green.conf file is in that Gist, but it looks to be a configuration file for some sort of DHCP server?)

That doesn't seem to be happening in my case. Here's a summary of all IPv4 UDP messages during the boot process:

Code:

12:52:05.223313 IP 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:4d:12:82, length 396
12:52:08.227723 IP 192.168.122.1.67 > 192.168.122.141.68: BOOTP/DHCP, Reply, length 300
12:52:13.132583 IP 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:4d:12:82, length 408
12:52:13.132728 IP 192.168.122.1.67 > 192.168.122.141.68: BOOTP/DHCP, Reply, length 300

Here's the decoded detail of of the DHCP reply:

Code:

12:52:08.227723 IP (tos 0xc0, ttl 64, id 30016, offset 0, flags [none], proto UDP (17), length 328)
    192.168.122.1.67 > 192.168.122.141.68: [udp sum ok] BOOTP/DHCP, Reply, length 300, xid 0xc841183d, secs 8, Flags [none] (0x0000)
      Your-IP 192.168.122.141
      Server-IP 192.168.122.1
      Client-Ethernet-Address 52:54:00:4d:12:82
      Vendor-rfc1048 Extensions
        Magic Cookie 0x63825363
        DHCP-Message Option 53, length 1: Offer
        Server-ID Option 54, length 4: 192.168.122.1
        Lease-Time Option 51, length 4: 3600
        RN Option 58, length 4: 1800
        RB Option 59, length 4: 3150
        Subnet-Mask Option 1, length 4: 255.255.255.0
        BR Option 28, length 4: 192.168.122.255
        Default-Gateway Option 3, length 4: 192.168.122.1
        Domain-Name-Server Option 6, length 4: 192.168.122.1

So no option appears to be telling iPXE not to try sending a DHCP request to port 4011.

Quote:regarding proxy dhcp there is a note at http://ipxe.org/cmd/ifconf#notes about something that is very similar to your issue

Yes, I had already looked at this page. I suspect the advice is a bit old; it looks as if the 1.x versions of iPXE already build in the appropriate delay for a proxy server to reply. You'll note in the dump above that there's a second DHCP request made five seconds after the first DHCP reply is received; there's also a several-second delay after that before iPXE returns to the command line. I'm guessing that this would be iPXE waiting for a separate DHCP response from a proxy DHCP server. Unfortunately, since it never sent out a response on port 4011, no response is generated.

(One solution I'd tried to check this out, BTW, was running the proxy DHCP server on port 67 on a different IP address, but unfortunately the primary DHCP server is configured to listen on port 67 on all addresses on the host, and so it grabs port 67 on the new address the instant I add that address to the system.)

Quote:But first of: https://git.ipxe.org/ipxe.git/commit/6366fa7a that version is over a year old, you should try and do dhcp && chain http://boot.ipxe.org/ipxe.pxe m the qemu provided ipxe since there have been lots of improvements (and we do not like to try and debug old versions)

Unfortunately I can't do that automatically unless I can get the darn thing to send a query to my proxy DHCP server, since changing the configuration of the DHCP server running on port 67 isn't practical in my situation. (In which case my problem would be solved, anyway, since the rest of the boot process works fine once I can get a filename to iPXE.)

So at this point it looks as if I'm stuck.

I did, however chainload the above link, which gave me a build from commit 4a4da (which is HEAD of the master branch from the Git repo) and examined its boot behaviour; it has the same problem as the 6366fa7a that came with QEMU: it never sends a request to port 4011.

I'm wondering, do I not properly understand the behaviour that's supposed to be happening here? Is a PXE client not supposed to be sending DHCP requests to port 4011 as well as port 63, by default?