[CentOS] UEFI and PXE

Sat Apr 27 00:24:27 UTC 2019
Chris Adams <linux at cmadams.net>

Once upon a time, isdtor <isdtor at gmail.com> said:
> 11:06:51.413549 IP (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 390)
>     10.1.2.2.67 > 255.255.255.255.68: [udp sum ok] BOOTP/DHCP, Reply, length 362, xid 0x4007adc6, Flags [Broadcast] (0x8000)
>           Your-IP 10.1.2.57
>           Server-IP 10.1.2.1                                      <--
>           Client-Ethernet-Address 00:1b:21:d8:69:1c
>           file "linux-install/bootx64.efi"
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             DHCP-Message Option 53, length 1: ACK
>             Server-ID Option 54, length 4: 10.1.2.2
>             Lease-Time Option 51, length 4: 43200
>             Subnet-Mask Option 1, length 4: 255.255.255.0
>             Default-Gateway Option 3, length 4: 10.1.2.250
>             Domain-Name-Server Option 6, length 8: 10.1.2.2
>             Hostname Option 12, length 5: "client"
>             Domain-Name Option 15, length 20: "foo.bar.com"
>             NTP Option 42, length 8: 10.1.2.2
>             RN Option 58, length 4: 21600
>             RB Option 59, length 4: 37800
>             TFTP Option 66, length 11: "10.1.2.1"                 <--
>             END Option 255, length 0

I do see a couple of differences - main one is that my boot file is in
option 67, not the BOOTP "file" field.  Also, my option 66 is a
hostname, not an IP.  I don't know how you tell ISC DHCP to use option
67 instead of the file field, but maybe that could trigger different
client behavior?

More odd is that dnsmasq is adding a null terminator to both options 66
and 67.  My UEFI PXE clients seem to accept it just fine though.

-- 
Chris Adams <linux at cmadams.net>