patchThe GNU Hurd - Patches: patch #6851, Reassigned to another tracker...

 
 

You are not allowed to post comments on this tracker with your current authentification level.

patch #6851: Reassigned to another tracker [was: fix a bug in BPF]

Submitted by:  Zheng Da <zhengda>
Submitted on:  Sun 21 Jun 2009 01:36:19 AM UTC  
 
Category: GNU MachPriority: 5 - Normal
Status: DonePrivacy: Public
Assigned to: Zheng Da <zhengda>Open/Closed: Closed
Planned Release: None
Wiki-like text discussion box: 

Wed 14 Oct 2009 08:07:33 AM UTC, comment #5:

THIS ITEM WAS REASSIGNED TO BUG #27698


Please, do not post any new comments to this item.

Thomas Schwinge <tschwinge>
Project Administrator
Thu 30 Jul 2009 03:25:21 AM UTC, comment #4:

The only user of packet_header that I can see is NPF. It requires more data copy in order to remove the packet_header before delivering the packet to the user space, I guess. but I don't understand the implementation of NPF.

Zheng Da <zhengda>
Project MemberIn charge of this item.
Wed 29 Jul 2009 09:04:49 AM UTC, comment #3:

> The packet delivered from gnumach should have the packet header. NPF returns the packet_header and pfinet always assumes that the packet from gnumach has the packet_header.


OK, I understand that, and it is fine, but is there a specific reason to send package_header to user-space? (That is, if it's not required, then we should perhaps change pfinet and net_filter to not handle it?) If I understand the code correctly, packets that go from pfinet to the kernel to be sent out, do not contain the packet_header, but packets that go from the kernel to pfinet do contain the packet_header. Why this asymmetry? Perhaps I fail to understand what this packet_header is actually good for. (All that is unrelated to this bug report, of course, but while we're at it...)

> For your first question, the return value of net_do_filter is boolean, i.e., it can only be passed or not passed, but bpf_do_filter returns the size of the data that passes the filter.


OK, I see. The code could be written in a way that this is more obvious... (15 years old code, I know.)

My question also was whether net_do_filter should be changed to not handle the packet_header-part of the packet, as that is not related to the actual packet data (as I understand it), and thus should not be involved in deciding whether to allow or deny a given packet. (That's also unrelated to this bug report.)

Given the same instructions as in bug #20612, please install this patch. (And then we can think about the other issues I'm talking above.)

Thomas Schwinge <tschwinge>
Project Administrator
Wed 29 Jul 2009 08:15:10 AM UTC, comment #2:

The packet delivered from gnumach should have the packet header. NPF returns the packet_header and pfinet always assumes that the packet from gnumach has the packet_header.

For your first question, the return value of net_do_filter is boolean, i.e., it can only be passed or not passed, but bpf_do_filter returns the size of the data that passes the filter.

bpf_do_filter(infp, net_kmsg(kmsg)->packet + sizeof(struct packet_header), count, net_kmsg(kmsg)->header, ifp->if_header_size, &hash_headp, &entp) is simply wrong because the length of the packet data passed to bpf_do_filter isn't 'count' any more.

Zheng Da <zhengda>
Project MemberIn charge of this item.
Tue 28 Jul 2009 12:53:10 PM UTC, comment #1:

I had a look at this. In general, the patch seems to be correct. Two questions: Why isn't the same adjustment being done for net_do_filter, or why doesn't it have to be done? Why do we (have to) return the packet_header to user-space?

Thomas Schwinge <tschwinge>
Project Administrator
Sun 21 Jun 2009 01:36:19 AM UTC, original submission:

THIS ITEM WAS REASSIGNED TO BUG #27698
The packet data passed to BPF should exclude the packet_header.
The amount of a packet that returns to the user space should include packet_header.

Zheng Da <zhengda>
Project MemberIn charge of this item.

 

No files currently attached

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -unavailable- added by tschwinge (Posted a comment)
  • -unavailable- added by zhengda (Submitted the item)
  •  

    Do you think this task is very important?
    If so, you can click here to add your encouragement to it.
    This task has 0 encouragements so far.

    Only logged-in users can vote.

     

    Please enter the title of George Orwell's famous dystopian book (it's a date):

     

     

    Follow 4 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Wed 14 Oct 2009 08:07:33 AM UTCtschwingeReassign ItemThe GNU Hurd, patch #6851=>The GNU Hurd, bug #27698
    Wed 14 Oct 2009 08:07:05 AM UTCtschwingeStatusWorks For Me=>Done
      Assigned toNone=>zhengda
    Sun 21 Jun 2009 01:36:20 AM UTCzhengdaAttached File-=>Added bpf.patch, #18298

    Back to the top


    Powered by Savane 3.1-cleanup