From nobody Tue Jan 20 10:37:16 2026 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4dwP0F03LYz6PMpQ for ; Tue, 20 Jan 2026 10:37:17 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R13" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4dwP0D6Xswz3Cps for ; Tue, 20 Jan 2026 10:37:16 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1768905436; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=qdym7IhN68lpcprCUtAH6qshgN9v2iFGTxBEobXOTWA=; b=v0AiMS5V7qrPpWskXQ4fZT0Bgn4gjkX0Ee1Ke05jhZXjvsVALE2EYHH4yhZUYW3IJDYVjx /7suf1RN23H8n1ahYZP6cUFt5oqSFsF2Q+TvH+8WelVU+l4zdPEcm1t3jj3qS7aw3LKvpw uV04oy1+oEQmo2Bro+Hy3qtn9Q9bY55zcnHLb1xyhkMPka+pnRzdcVmx1yeJIo8Ydpx6Ju 61K6aBENGY869ge3Oa8TDTUtwvgIwxDs1gG3F0SiBNjxHzK1NS2SOJ7zqfxhpGSr7y+t6Z 07IIfDPzyZJ/HVyZPDrgyyMXFU3qSNqESsJuOvd3/xMzFZafJaC2L0P2Nr6t+w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1768905436; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=qdym7IhN68lpcprCUtAH6qshgN9v2iFGTxBEobXOTWA=; b=WIN2hXR59Wmmg40I5h6aPWzY4/GJYlW48kZN//qlWqYTHWjwbSvPSRHMxWKeLaTuIqkoTF WcE76wzGUdRqPTWPddGoOkvtF7br9Q6uyn7+HAaGpvaxMo5g1B4Bm3XrgO6IZ0UjQnmWWH ccKTn2lsCaeUYtLccc1nxymOSlgmotr1LRSIU6O7DPnRgvm6gm4YOKH2MouB079To0ukDZ kG6p37nilbjnMi36z+EPFD0u0jJhNfFeGSjDbvKSDvVocZB7FPPwyHuQgESjBiOs6YTRFF DNrGwmR14fMcd3XTG1bfBhiSlyt8l8FYl4t/s0sGb4U5AQflXqjElWl6f1hSHg== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1768905436; a=rsa-sha256; cv=none; b=Qv3eFupipHsZpGdfj2nZkaGkXI+JZA8Wfx7bexfuxL2PXpDBKpQpGffr41S0XZAyAiqmaW zGfIWqjfCEmGvAVCCc6GfLwKh4Hd69TKa3/uKt1mj1SAqxEO+ft9RW/jMO0/XZoeFwJ31Y UoDHw/OBBIE7DnNAWIMn1eupHPzsGV8iRDSIVOOKWl98vFgNU5PUYVQaLoT8c6TjyOgezB Ki5d03x8/uTThlY8jiyJWCbNS8+5ij5nV5tWtTcfIteQ89U8qrPsl04UaCgkeZ8zGaxfu2 mrxQEKojUk7LYTQqrNXsraRwqZ57L/Nmo248XIpQEqqTXnplS1HND949lUgzEQ== ARC-Authentication-Results: i=1; mx1.freebsd.org; none Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4dwP0D64SNz1CXk for ; Tue, 20 Jan 2026 10:37:16 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 37534 by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Tue, 20 Jan 2026 10:37:16 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Cc: Timo =?utf-8?Q?V=C3=B6lker?= From: Michael Tuexen Subject: git: 6f15ba8004c3 - main - ip: improve deferred computation of checksums List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: tuexen X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 6f15ba8004c3fdc2fb12f0cd6618d1b3a40aab7d Auto-Submitted: auto-generated Date: Tue, 20 Jan 2026 10:37:16 +0000 Message-Id: <696f5adc.37534.64e386d7@gitrepo.freebsd.org> The branch main has been updated by tuexen: URL: https://cgit.FreeBSD.org/src/commit/?id=6f15ba8004c3fdc2fb12f0cd6618d1b3a40aab7d commit 6f15ba8004c3fdc2fb12f0cd6618d1b3a40aab7d Author: Timo Völker AuthorDate: 2026-01-20 10:30:19 +0000 Commit: Michael Tuexen CommitDate: 2026-01-20 10:36:40 +0000 ip: improve deferred computation of checksums This patch adds the same functionality for the IPv4 header checksum as was done erlier for the SCTP/TCP/UDP transport checksum. When the IP implementation sends a packet, it does not compute the corresponding checksum but defers that. It will determine whether the network interface selected for the packet has the requested capability and computes the checksum in software, if the selected network interface does not have the requested capability. Do this not only for packets being sent by the local IP stack, but also when forwarding packets. Furthermore, when such packets are delivered to a local IP stack, do not compute or validate the checksum, since such packets have never been on the wire. This allows to support checksum offloading also in the case of local virtual machines or jails. Support for epair interfaces will be added in a separate commit. Reviewed by: pouria, tuexen MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D54455 --- share/man/man9/mbuf.9 | 5 +++-- sys/netinet/ip_fastfwd.c | 32 +++++++++++++++++++++++--------- sys/netinet/ip_input.c | 6 ++++++ 3 files changed, 32 insertions(+), 11 deletions(-) diff --git a/share/man/man9/mbuf.9 b/share/man/man9/mbuf.9 index e4f30962ccab..265a6dddda98 100644 --- a/share/man/man9/mbuf.9 +++ b/share/man/man9/mbuf.9 @@ -22,7 +22,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd August 1, 2025 +.Dd January 20, 2026 .Dt MBUF 9 .Os .\" @@ -1216,13 +1216,14 @@ in is not set, since SCTP does not use a pseudo header checksum. .Pp If IP delivers a packet with the flags +.Dv CSUM_IP , .Dv CSUM_SCTP , .Dv CSUM_TCP , or .Dv CSUM_UDP set in .Va csum_flags -to a local SCTP, TCP, or UDP stack, the packet will be processed without +to a local IP, SCTP, TCP, or UDP stack, the packet will be processed without computing or validating the checksum, since the packet has not been on the wire. This can happen if the packet was handled by a virtual interface such as diff --git a/sys/netinet/ip_fastfwd.c b/sys/netinet/ip_fastfwd.c index d3d42afb2d84..6001ce781bc8 100644 --- a/sys/netinet/ip_fastfwd.c +++ b/sys/netinet/ip_fastfwd.c @@ -359,15 +359,20 @@ passin: } /* - * Decrement the TTL and incrementally change the IP header checksum. - * Don't bother doing this with hw checksum offloading, it's faster - * doing it right here. + * Decrement the TTL. + * If the IP header checksum field contains a valid value, incrementally + * change this value. Don't use hw checksum offloading, which would + * recompute the checksum. It's faster to just change it here + * according to the decremented TTL. + * If the checksum still needs to be computed, don't touch it. */ ip->ip_ttl -= IPTTLDEC; - if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) - ip->ip_sum -= ~htons(IPTTLDEC << 8); - else - ip->ip_sum += htons(IPTTLDEC << 8); + if (__predict_true((m->m_pkthdr.csum_flags & CSUM_IP) == 0)) { + if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) + ip->ip_sum -= ~htons(IPTTLDEC << 8); + else + ip->ip_sum += htons(IPTTLDEC << 8); + } #ifdef IPSTEALTH } #endif @@ -465,9 +470,18 @@ passout: gw = (const struct sockaddr *)dst; /* - * If TCP/UDP header still needs a valid checksum and interface will not - * calculate it for us, do it here. + * If the IP/SCTP/TCP/UDP header still needs a valid checksum and the + * interface will not calculate it for us, do it here. + * Note that if we defer checksum calculation, we might send an ICMP + * message later that reflects this packet, which still has an + * invalid checksum. */ + if (__predict_false(m->m_pkthdr.csum_flags & CSUM_IP & + ~nh->nh_ifp->if_hwassist)) { + ip->ip_sum = 0; + ip->ip_sum = in_cksum(m, (ip->ip_hl << 2)); + m->m_pkthdr.csum_flags &= ~CSUM_IP; + } if (__predict_false(m->m_pkthdr.csum_flags & CSUM_DELAY_DATA & ~nh->nh_ifp->if_hwassist)) { in_delayed_cksum(m); diff --git a/sys/netinet/ip_input.c b/sys/netinet/ip_input.c index 2e0635f8e482..1e1747d04c45 100644 --- a/sys/netinet/ip_input.c +++ b/sys/netinet/ip_input.c @@ -532,6 +532,12 @@ ip_input(struct mbuf *m) if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) { sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID); + } else if (m->m_pkthdr.csum_flags & CSUM_IP) { + /* + * Packet from local host that offloaded checksum computation. + * Checksum not required since the packet wasn't on the wire. + */ + sum = 0; } else { if (hlen == sizeof(struct ip)) { sum = in_cksum_hdr(ip);