回复: [edk2-devel] [PATCH v1] NetworkPkg/UefiPxeBcDxe: Fix PXE_BOOT_SERVERS usage in boot info parse flow

["Ding, Seven" <Seven.ding@lcfuturecenter.com>]

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Thank you for your attention to this issue,  current status we already fix our customer problem, but we don’t know the root cause  whether related to server  configuration or EDK2 code.

I have no concerns with close TianoCore#2876 as INVALID

Thank you all.





Attached package is server configuration files,   PSW: 123

How to reproduce:

1. Prepare three machines for server and a switch with at least 4 LAN ports (you can also use a router instead). The machine will use Windows 10 system

2. Connect all three machines to the switch with a network cable. The switch does not need to be connected to an external network.

3. Turn off the firewalls on each machine

4. Set the static Address of the first machine to 192.168.20.2, extract the TFTP.rAR package and copy it to the root directory of Disk C, click Serva32. exe and wait for 7 seconds, then click "Thanks, not today..." The button

5. Set the second machine static IP 192.168.20.100, extract dhCp.rar and copy it to the root directory of Disk C, and click Serva32.exe

6. Set the third machine static IP 192.168.20.10, extract copy of proxydhcp.rar and proxydhcpworking. Rar to the root directory of Disk C, just click serva32.exe in the proxydhCP folder

7. Ping the machines to make sure they are connected

8. To prepare a fourth machine, connected to the switch.

9. Set UEFI only Mode in the BIOS (the fourth machine ) , Restart the machine press F12 to enter the boot page and select PXE Boot.

you will see the fourth machine connect to proxydhcp-> problem





problem:

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Expection:





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-----邮件原件-----
发件人: Laszlo Ersek <lersek@redhat.com>
发送时间: Friday, August 21, 2020 5:11 PM
收件人: Michael Brown <mcb30@ipxe.org>; devel@edk2.groups.io; maciej.rabeda@linux.intel.com
抄送: Jiaxin Wu <jiaxin.wu@intel.com>; Siyuan Fu <siyuan.fu@intel.com>; Ding, Seven <Seven.ding@lcfuturecenter.com>
主题: Re: [edk2-devel] [PATCH v1] NetworkPkg/UefiPxeBcDxe: Fix PXE_BOOT_SERVERS usage in boot info parse flow



On 08/20/20 15:41, Michael Brown wrote:

> On 20/08/2020 11:44, Maciej Rabeda wrote:

>> @Michael

>> I am now wondering whether bit 3 is actually relevant to server choice.

>>

>> Bit 3:

>> == 0 -> prompt user to choose a boot file. Which means to me: show

>> minimal menu with prompt (tag 10 - PXE_MENU_PROMPT) and options (tag 9

>> - PXE_BOOT_MENU).

>> == 1 -> do not prompt user. If boot file name is present (option 67),

>> download that boot file.

>>

>> Bit 3 does not seem to specify/regulate which server to use.

>>

>> Choice of server IP might look like:

>>

>> if (option 43 is present, tag 6 is present, tag_6.bit_2 is set and tag

>> 8 is present and valid)

>>          take server IP from tag 8 (PXE_BOOT_SERVERS)

>>

>> else if (option 66 is present)

>>          take server IP from option 66 (TFTP server name)

>>

>> else if (option 54 is present)

>>          take server IP from option 54 (Server Identifier)

>>

>> else

>>          failure

>

> RFC 2132 defines option 66 as a hostname (not an IP address): it is the

> equivalent of the non-option "sname" field.

>

> RFC 2132 defines option 54 as the DHCP server identifier, which is

> unrelated to the TFTP server.

>

> In the simple case (with no PXE menus involved), the TFTP server IP is

> provided by the non-option "siaddr" field.

>

> If option 60 is set to "PXEClient" and option 43 tag 9 is present and

> option 43 tag 6 bit 3 is clear then this initiates a convoluted process

> in which the user is first presented with an interactive menu

> (constructed from the contents of option 43 tag 9) in order to select a

> "boot server type", after which a second convoluted process is performed

> to query the network using a protocol that is almost, but not quite,

> entirely unlike DHCP.  The TFTP server IP and boot filename are

> eventually taken from the selected response packet in this final

> almost-DHCP exchange.



*shudder*



I'll 100% defer to you and Maciej on this -- this is very complicated.



To begin with, I'm not fully clear what the purpose of edk2 git commit

ecec42044078 ("Update PXE driver to support PXE forced mode.",

2014-01-06) was.



What on Earth is "PXE forced mode"?



Siyuan, can you please explain?



And then I don't know whether the bug report at



  https://bugzilla.tianocore.org/show_bug.cgi?id=2876



really has merit.



In the words of the reporter, the presently discussed patch would still

qualify as a "work-around", for making the PXE client ignore

PXE_BOOT_SERVERS, via clearing option#43 tag#6 bit#2 in the DHCP server

response. But IMO the more important question is whether it is valid for

the DHCP server (config) at their site to (a) populate PXE_BOOT_SERVERS,

(b) put (apparently!) the ProxyDHCP IP address in PXE_BOOT_SERVERS.



Like, I'd like to be convinced that the server config at the reporter's

site is not *invalid* in the first place. If it's invalid, then we

shouldn't be complicating the edk2 client code with a workaround. Even

if we adopted the workaround, the reporter would still have to

*activate* it, by manually clearing the bit in question (see at the very

end of <https://bugzilla.tianocore.org/show_bug.cgi?id=2876#c4>).



For me one big difficulty is that the PXE config options are scattered

about a forest of specs. Last time I spent more than an hour cursing and

hunting for them.



At Red Hat, over the last few years I've received an immense amount of

bug reports related to PXEv4/PXEv6 booting with edk2. In almost every

case, it was a bug in the reporter's server configuration. Yes,

anecdotal evidence. It makes me very reluctant to change the edk2 code,

especially that the reporter of TianoCore#2876 has seemingly stopped

communications.



Note how the bug report makes references to various attachments, such as

RAR files and one "Serva32.exe", regarding a reproducer. But until now,

with the latest comment being #9, those files have *not* been attached.

So it's not like we can set up some virtual machines on a virtual

network and fire up wireshark or tcpdump, to see the actual traffic.



I'm happy to pull out of this review session, as I trust you Michael and

Maciej to do the right here. I'm happy to offer some level of regression

testing, if you got new patches. I'd also be OK to simply close

TianoCore#2876 as INVALID (due to insufficient data).



Thanks

Laszlo



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