From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH] Revert "net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends" Date: Fri, 15 Jun 2018 12:14:32 -0700 Message-ID: References: <20180615185645.8921-1-malat@debian.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: Mathieu Malaterre , "David S. Miller" Return-path: In-Reply-To: <20180615185645.8921-1-malat@debian.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 06/15/2018 11:56 AM, Mathieu Malaterre wrote: > This reverts commit 88078d98d1bb085d72af8437707279e203524fa5. > > It causes regressions for people using chips driven by the sungem > driver. Suspicion is that the skb->csum value isn't being adjusted > properly. > > Symptoms as seen on G4+sungem are: > > [ 34.023281] eth0: hw csum failure > [ 34.023438] CPU: 0 PID: 0 Comm: swapper Not tainted 4.17.0+ #2 > [ 34.023618] Call Trace: > [ 34.023707] [dffedbd0] [c069ddac] __skb_checksum_complete+0xf0/0x108 (unreliable) > [ 34.023948] [dffedbf0] [c0777a70] tcp_v4_rcv+0x604/0xe00 > [ 34.024118] [dffedc70] [c0731624] ip_local_deliver_finish+0xa8/0x3c4 > [ 34.024315] [dffedcb0] [c0732430] ip_local_deliver+0xf0/0x154 > [ 34.024493] [dffedcf0] [c07328dc] ip_rcv+0x448/0x774 > [ 34.024653] [dffedd50] [c06aeae0] __netif_receive_skb_core+0x5e8/0x1184 > [ 34.024857] [dffedde0] [c06bba20] napi_gro_receive+0x160/0x22c > [ 34.025044] [dffede10] [e14b2590] gem_poll+0x7fc/0x1ac0 [sungem] > [ 34.025228] [dffedee0] [c06bacf0] net_rx_action+0x34c/0x618 > [ 34.025402] [dffedf60] [c07fd27c] __do_softirq+0x16c/0x5f0 > [ 34.025575] [dffedfd0] [c0064c7c] irq_exit+0x110/0x1a8 > [ 34.025738] [dffedff0] [c0016170] call_do_irq+0x24/0x3c > [ 34.025903] [c0cf7e80] [c0009a84] do_IRQ+0x98/0x1a0 > [ 34.026055] [c0cf7eb0] [c001b474] ret_from_except+0x0/0x14 > [ 34.026225] --- interrupt: 501 at arch_cpu_idle+0x30/0x78 > LR = arch_cpu_idle+0x30/0x78 > [ 34.026510] [c0cf7f70] [c0cf6000] 0xc0cf6000 (unreliable) > [ 34.026682] [c0cf7f80] [c00a3868] do_idle+0xc4/0x158 > [ 34.026835] [c0cf7fb0] [c00a3ab0] cpu_startup_entry+0x20/0x28 > [ 34.027013] [c0cf7fc0] [c0998820] start_kernel+0x47c/0x490 > [ 34.027181] [c0cf7ff0] [00003444] 0x3444 > > See commit 7ce5a27f2ef8 ("Revert "net: Handle CHECKSUM_COMPLETE more > adequately in pskb_trim_rcsum()."") for previous reference. This fix seems to hide a bug in csum functions on this architecture. Or a bug on this NIC when receiving a small packet (less than 60 bytes). Maybe the padding bytes are not included in NIC provided csum, and not 0.