From nobody Sun Apr 26 07:45:07 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 4g3JdN2YYxz6bB8k for ; Sun, 26 Apr 2026 07:45:12 +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" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4g3JdN20CKz40Pt for ; Sun, 26 Apr 2026 07:45:12 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1777189512; 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=Ha73fl7Yfjo6e4W0ceBIz0yLTjjQMqw3q0RRdoC5B9A=; b=LfZgaXgKkqJCQHZgORESoUOFMX1dkBL5FHDEivjcTVwKxfpolopc/K+GFuk4Nc8zeugdxQ TpGLCE8or2hoG6pruhENevXpUaSQ3YG60A4bQKgQPeU6HVmcOUE50gdY+zSsS9l0i5Vm8C PUtIMnnLQph58C3tR504HNSV6SsOJY/E6dfPKCNiwd9zeHRWroZcvzEKINmyEt+HQFJVOT h+RHP86PfwXQzxpqp1oAuepv0V+LSw9ncnOrVMALFNpAuZXjfkgbE08R7CVQnwxp7xgzwh 6fupWEL1u5rouEp1oXNZVyTnJjo7WQZT8+v2wwbfd/bdmt5MKdZxy1Phvi/TOw== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1777189512; a=rsa-sha256; cv=none; b=XFgUbD52X9WnFhjFUy4ma4J8oIyiPzeTmu8lM3+a1ad5b6suqHGe6XZGXbN5Y0jegrQM8T vNmUVPyIPbASGC7bYmpnyTpc+YY3UU1clF2AV1hodRH+VFiXlPdefP9+nxJR8nkwOMuHyO VDsNA598HHP429A3UdYGfW5LfROw/tHl7trar8WsB7YJxnNT7xuGzIKS/k7J85g3+Oi5dX dGNLcHOWIdKw0v4UJqkL5M3IT4z0RMxKW92JqOHdjEXJbUuOnExPvMF/nHsL3iLWmgyfKJ NbMaSAGSDkCtebDqZ6bfwYiDi01/G3/xmdmxgmGd6evvocpgvyLarJVJ/aMyVg== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1777189512; 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=Ha73fl7Yfjo6e4W0ceBIz0yLTjjQMqw3q0RRdoC5B9A=; b=vxIqClc5YH2yG42D8UvLe2eHHfNW7mqoRHSG5QviUzsL9ttYjJA36PiqsZ5p9T6DJUq0H2 RkAlyGKbP2a5rxPQxlqu8fUBM0njXTfxJViC+kTuopAhZTsnpWauEW/oRHxOnGtMtbHOpL 1KrBJiUpXjEgxyY9oYkativ+qzLOmn0ISlNtKbBFIRCOACCIfHIxtNJzikf3yZPMhlpZkj ajOLo6Xi0DxBjbu4x+WPrHNmOothsr8RfXTeWIPGiZmB1YwEMmStoUCkCzybpA8GbUzENY +9lP8487GmH528xqrxHnIskL188Pc53ogvYDhwEYWOo8JudyOj9Kenl4CYovxg== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4g3JdN1Thvz19CG for ; Sun, 26 Apr 2026 07:45:12 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 253d2 by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Sun, 26 Apr 2026 07:45:07 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Cc: Timo =?utf-8?Q?V=C3=B6lker?= From: Michael Tuexen Subject: git: bba71b3f7c15 - stable/15 - 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/stable/15 X-Git-Reftype: branch X-Git-Commit: bba71b3f7c1561fd40d279001536540f43c707c4 Auto-Submitted: auto-generated Date: Sun, 26 Apr 2026 07:45:07 +0000 Message-Id: <69edc283.253d2.757126ff@gitrepo.freebsd.org> The branch stable/15 has been updated by tuexen: URL: https://cgit.FreeBSD.org/src/commit/?id=bba71b3f7c1561fd40d279001536540f43c707c4 commit bba71b3f7c1561fd40d279001536540f43c707c4 Author: Timo Völker AuthorDate: 2026-01-20 10:30:19 +0000 Commit: Michael Tuexen CommitDate: 2026-04-26 07:42:55 +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 Differential Revision: https://reviews.freebsd.org/D54455 Event: Wiesbaden Hackathon 2026 (cherry picked from commit 6f15ba8004c3fdc2fb12f0cd6618d1b3a40aab7d) --- 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 c567d28f24f0..ecba083dbb77 100644 --- a/sys/netinet/ip_fastfwd.c +++ b/sys/netinet/ip_fastfwd.c @@ -360,15 +360,20 @@ 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 @@ -466,9 +471,18 @@ 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 652aa4a99e79..cc7b35f5d168 100644 --- a/sys/netinet/ip_input.c +++ b/sys/netinet/ip_input.c @@ -525,6 +525,12 @@ 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);