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[76.103.20.67]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2156b1601basm59404425ad.196.2024.12.03.14.35.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Dec 2024 14:35:40 -0800 (PST) Date: Tue, 3 Dec 2024 14:35:38 -0800 From: Frederik Deweerdt To: Cong Wang Cc: David Howells , netdev@vger.kernel.org Subject: Re: [PATCH net] splice: do not checksum AF_UNIX sockets Message-ID: References: <537172.1733243422@warthog.procyon.org.uk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Dec 03, 2024 at 01:48:56PM -0800, Cong Wang wrote: > On Tue, Dec 03, 2024 at 04:30:22PM +0000, David Howells wrote: > > Frederik Deweerdt wrote: > > > > > - if (skb->ip_summed == CHECKSUM_NONE) > > > + if (skb->ip_summed == CHECKSUM_NONE && skb->sk->sk_family != AF_UNIX) > > > skb_splice_csum_page(skb, page, off, part); > > > > Should AF_UNIX set some other CHECKSUM_* constant indicating that the checksum > > is unnecessary? > > > > It already means unnecessary on TX path: > > * - %CHECKSUM_NONE > * > * The skb was already checksummed by the protocol, or a checksum is not > * required. > Looking back at the patch series that introduced the checksumming [1], it looks like `ip_output.c::ip_append_page()` was the only path doing checksumming, it had similar looking logic: - - if (skb->ip_summed == CHECKSUM_NONE) { - __wsum csum; - csum = csum_page(page, offset, len); - skb->csum = csum_block_add(skb->csum, csum, skb->len); - } - That code in turn has been like this since the git import. I'm not sure what that was for and how to test its intent. Frederik [1] https://patchwork.kernel.org/project/linux-mm/patch/20230522121125.2595254-15-dhowells@redhat.com/