On Fri, 18 Jun 2021 15:03:59 +0000 Arijit De wrote:
Hi,
In the latest linux kernel (i.e. 5.12.x) I am observing that for my
Ethernet driver ping test has stopped working, it was working in
5.4.x and all the older kernels. I have debugged the issue and root
caused that it's because of the recent commit
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8f9a69a92fc63917c9bd921b28e3b2912980becf
In my Network card HW it supports checksum offload for IPv4 frame,
but it can't verify checksum for the ICMP frames, so I use
CHECKSUM_PARTIAL in the skb->ip_summed for this kind of scenario.
Do you mean that your drivers sets up CHECKSUM_PARTIAL on Rx? If HW
hasn't validated the checksum just leave the skb with CHECKSUM_NONE,
the stack will validate.
But now because of this new logic what you have added ping frames are
getting dropped.
My Ping packets skb dump:
[112241.545219] skb len=88 headroom=78 headlen=0 tailroom=0
[112241.545219] mac=(64,-64) net=(0,-1) trans=-1
[112241.545219] shinfo(txflags=0 nr_frags=1 gso(size=0 type=0 segs=0))
[112241.545219] csum(0x0 ip_summed=3 complete_sw=0 valid=0 level=0)
[112241.545219] hash(0x0 sw=0 l4=0) proto=0x0800 pkttype=0 iif=0
[112241.572837] dev name=enp137s0 feat=0x0x0000010000004813
[112241.578141] skb headroom: 00000000: 4c 00 70 35 09 de b4 e4 00 11
22 33 44 01 08 06 [112241.585876] skb headroom: 00000010: 00 01 08 00
06 04 00 02 00 11 22 33 44 01 0a 1c [112241.593611] skb headroom:
00000020: 28 13 70 35 09 de b4 e4 0a 1c 28 01 00 00 00 00
[112241.601345] skb headroom: 00000030: 50 04 00 00 55 50 00 00 14 00
03 00 00 00 00 00 [112241.609080] skb headroom: 00000040: 00 11 22 33
44 01 ac 1f 6b d2 c0 e5 08 00 [112241.616293] skb frag: 00000000:
45 00 00 54 87 a2 40 00 40 01 4d e3 0a 1c 28 d9 [112241.624027] skb
frag: 00000010: 0a 1c 28 13 08 00 fd 50 0c a8 00 03 6a 94 cc 60
[112241.631762] skb frag: 00000020: 00 00 00 00 f5 3b 03 00 00 00
00 00 10 11 12 13 [112241.639496] skb frag: 00000030: 14 15 16 17
18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 [112241.647230] skb frag:
00000040: 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33
[112241.654965] skb frag: 00000050: 34 35 36 37 9c b0 19 b9
Its hitting the check for CHECKSUM_PARTIAL in pskb_trim_rcsum_slow()
and getting dropped there. Can you please let me know how can I
satisfy the requirement such that I can keep supporting the
CHECKSUM_PARTIAL cases for my network card ? I have checked
include/linux/skbuff.h For the documentation of CHECKSUM_PARTIAL, but
could not understand what change I have to do to make it working
again. My network driver is not up streamed yet in the linux kernel.
For any more information please do let me know.
Hi Jakub,
In my network card HW it can verify the received frame's checksum of IPv4 header, but it can't verify the checksum of ICMP header.
So for ICMP kind of received frames driver sets the checksum state to CHECKSUM_PARTIAL in skb->ip_summed. Which is as per the linux kernel documentation also.
Now before the commit https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8f9a69a92fc63917c9bd921b28e3b2912980becf this use case was working.
But now after introducing this logic for CHECKSUM_PARTIAL case, my received ICMP ping frames are getting dropped in the linux kernel pskb_trim_rcsum_slow().
I do understand that to bypass this scenario I can use CHECKSUM_NONE, but in that case HW's capability where checksum is already verified for the IPv4 header will be unutilized.
So please do share if any documentation update has happened for the CHECKSUM_PARTIAL scenario or please do let me know what need to be updated in the skb for the receive frame in this scenario where only Networking layer (i.e. IPv4 in this case) checksum is verified but the ICMP(ping) header checksum is not verified ?
Thanks
Arijit
-----Original Message-----
From: Jakub Kicinski <kuba@kernel.org>
Sent: Saturday, June 19, 2021 3:50 AM
To: Arijit De <redacted>
Cc: netdev@vger.kernel.org
Subject: [EXT] Re: Ping frame drop
External Email
----------------------------------------------------------------------
On Fri, 18 Jun 2021 15:03:59 +0000 Arijit De wrote:
Hi,
In the latest linux kernel (i.e. 5.12.x) I am observing that for my
Ethernet driver ping test has stopped working, it was working in 5.4.x
and all the older kernels. I have debugged the issue and root caused
that it's because of the recent commit
https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.org_pu
b_scm_linux_kernel_git_stable_linux.git_commit_-3Fid-3D8f9a69a92fc6391
7c9bd921b28e3b2912980becf&d=DwICAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=TaxnDgE1
8KxGhqsUtny5eMiBbXC81IdotAx6pqBUXWE&m=llYaO7Eowy-EL2vj6Lr3tV6AWHL1zodg
flS7funQd3I&s=fkqonnyQCEHc929sQLcwua-9L5utQkXp_kAr73NhQiA&e=
In my Network card HW it supports checksum offload for IPv4 frame, but
it can't verify checksum for the ICMP frames, so I use
CHECKSUM_PARTIAL in the skb->ip_summed for this kind of scenario.
Do you mean that your drivers sets up CHECKSUM_PARTIAL on Rx? If HW hasn't validated the checksum just leave the skb with CHECKSUM_NONE, the stack will validate.
But now because of this new logic what you have added ping frames are
getting dropped.
My Ping packets skb dump:
[112241.545219] skb len=88 headroom=78 headlen=0 tailroom=0
[112241.545219] mac=(64,-64) net=(0,-1) trans=-1 [112241.545219]
shinfo(txflags=0 nr_frags=1 gso(size=0 type=0 segs=0)) [112241.545219]
csum(0x0 ip_summed=3 complete_sw=0 valid=0 level=0) [112241.545219]
hash(0x0 sw=0 l4=0) proto=0x0800 pkttype=0 iif=0 [112241.572837] dev
name=enp137s0 feat=0x0x0000010000004813 [112241.578141] skb headroom:
00000000: 4c 00 70 35 09 de b4 e4 00 11
22 33 44 01 08 06 [112241.585876] skb headroom: 00000010: 00 01 08 00
06 04 00 02 00 11 22 33 44 01 0a 1c [112241.593611] skb headroom:
00000020: 28 13 70 35 09 de b4 e4 0a 1c 28 01 00 00 00 00
[112241.601345] skb headroom: 00000030: 50 04 00 00 55 50 00 00 14 00
03 00 00 00 00 00 [112241.609080] skb headroom: 00000040: 00 11 22 33
44 01 ac 1f 6b d2 c0 e5 08 00 [112241.616293] skb frag: 00000000:
45 00 00 54 87 a2 40 00 40 01 4d e3 0a 1c 28 d9 [112241.624027] skb
frag: 00000010: 0a 1c 28 13 08 00 fd 50 0c a8 00 03 6a 94 cc 60
[112241.631762] skb frag: 00000020: 00 00 00 00 f5 3b 03 00 00 00
00 00 10 11 12 13 [112241.639496] skb frag: 00000030: 14 15 16 17
18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 [112241.647230] skb frag:
00000040: 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33
[112241.654965] skb frag: 00000050: 34 35 36 37 9c b0 19 b9
Its hitting the check for CHECKSUM_PARTIAL in pskb_trim_rcsum_slow()
and getting dropped there. Can you please let me know how can I
satisfy the requirement such that I can keep supporting the
CHECKSUM_PARTIAL cases for my network card ? I have checked
include/linux/skbuff.h For the documentation of CHECKSUM_PARTIAL, but
could not understand what change I have to do to make it working
again. My network driver is not up streamed yet in the linux kernel.
For any more information please do let me know.
Please don't top post.
On Sat, 19 Jun 2021 15:14:35 +0000 Arijit De wrote:
In my network card HW it can verify the received frame's checksum of
IPv4 header, but it can't verify the checksum of ICMP header.
Linux does not offload IPv4 header checksums.
So for
ICMP kind of received frames driver sets the checksum state to
CHECKSUM_PARTIAL in skb->ip_summed. Which is as per the linux kernel
documentation also.
What documentation are you reading? Setting ip_summed to PARTIAL on
receive is only valid for software/virtual devices, never real HW.
Now before the commit
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8f9a69a92fc63917c9bd921b28e3b2912980becf
this use case was working. But now after introducing this logic for
CHECKSUM_PARTIAL case, my received ICMP ping frames are getting
dropped in the linux kernel pskb_trim_rcsum_slow(). I do understand
that to bypass this scenario I can use CHECKSUM_NONE, but in that
case HW's capability where checksum is already verified for the IPv4
header will be unutilized.
So please do share if any documentation update has happened for the
CHECKSUM_PARTIAL scenario or please do let me know what need to be
updated in the skb for the receive frame in this scenario where only
Networking layer (i.e. IPv4 in this case) checksum is verified but
the ICMP(ping) header checksum is not verified ?