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[82.64.211.94]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48febe7e442sm129500495e9.33.2026.05.20.07.52.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 May 2026 07:52:36 -0700 (PDT) Message-ID: <5506790a-ddf8-48cb-bd93-573de5f19822@redhat.com> Date: Wed, 20 May 2026 16:52:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/4] tcp_vu: Support multibuffer frames in tcp_vu_send_flag() To: David Gibson References: <20260416161618.3826904-1-lvivier@redhat.com> <20260416161618.3826904-5-lvivier@redhat.com> From: Laurent Vivier Autocrypt: addr=lvivier@redhat.com; keydata= xsFNBFYFJhkBEAC2me7w2+RizYOKZM+vZCx69GTewOwqzHrrHSG07MUAxJ6AY29/+HYf6EY2 WoeuLWDmXE7A3oJoIsRecD6BXHTb0OYS20lS608anr3B0xn5g0BX7es9Mw+hV/pL+63EOCVm SUVTEQwbGQN62guOKnJJJfphbbv82glIC/Ei4Ky8BwZkUuXd7d5NFJKC9/GDrbWdj75cDNQx UZ9XXbXEKY9MHX83Uy7JFoiFDMOVHn55HnncflUncO0zDzY7CxFeQFwYRbsCXOUL9yBtqLer Ky8/yjBskIlNrp0uQSt9LMoMsdSjYLYhvk1StsNPg74+s4u0Q6z45+l8RAsgLw5OLtTa+ePM JyS7OIGNYxAX6eZk1+91a6tnqfyPcMbduxyBaYXn94HUG162BeuyBkbNoIDkB7pCByed1A7q q9/FbuTDwgVGVLYthYSfTtN0Y60OgNkWCMtFwKxRaXt1WFA5ceqinN/XkgA+vf2Ch72zBkJL RBIhfOPFv5f2Hkkj0MvsUXpOWaOjatiu0fpPo6Hw14UEpywke1zN4NKubApQOlNKZZC4hu6/ 8pv2t4HRi7s0K88jQYBRPObjrN5+owtI51xMaYzvPitHQ2053LmgsOdN9EKOqZeHAYG2SmRW LOxYWKX14YkZI5j/TXfKlTpwSMvXho+efN4kgFvFmP6WT+tPnwARAQABzSNMYXVyZW50IFZp dmllciA8bHZpdmllckByZWRoYXQuY29tPsLBeAQTAQIAIgUCVgVQgAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjwpgg//fSGy0Rs/t8cPFuzoY1cex4limJQfReLr SJXCANg9NOWy/bFK5wunj+h/RCFxIFhZcyXveurkBwYikDPUrBoBRoOJY/BHK0iZo7/WQkur 6H5losVZtrotmKOGnP/lJYZ3H6OWvXzdz8LL5hb3TvGOP68K8Bn8UsIaZJoeiKhaNR0sOJyI YYbgFQPWMHfVwHD/U+/gqRhD7apVysxv5by/pKDln1I5v0cRRH6hd8M8oXgKhF2+rAOL7gvh jEHSSWKUlMjC7YwwjSZmUkL+TQyE18e2XBk85X8Da3FznrLiHZFHQ/NzETYxRjnOzD7/kOVy gKD/o7asyWQVU65mh/ECrtjfhtCBSYmIIVkopoLaVJ/kEbVJQegT2P6NgERC/31kmTF69vn8 uQyW11Hk8tyubicByL3/XVBrq4jZdJW3cePNJbTNaT0d/bjMg5zCWHbMErUib2Nellnbg6bc 2HLDe0NLVPuRZhHUHM9hO/JNnHfvgiRQDh6loNOUnm9Iw2YiVgZNnT4soUehMZ7au8PwSl4I KYE4ulJ8RRiydN7fES3IZWmOPlyskp1QMQBD/w16o+lEtY6HSFEzsK3o0vuBRBVp2WKnssVH qeeV01ZHw0bvWKjxVNOksP98eJfWLfV9l9e7s6TaAeySKRRubtJ+21PRuYAxKsaueBfUE7ZT 7zfOwU0EVgUmGQEQALxSQRbl/QOnmssVDxWhHM5TGxl7oLNJms2zmBpcmlrIsn8nNz0rRyxT 460k2niaTwowSRK8KWVDeAW6ZAaWiYjLlTunoKwvF8vP3JyWpBz0diTxL5o+xpvy/Q6YU3BN efdq8Vy3rFsxgW7mMSrI/CxJ667y8ot5DVugeS2NyHfmZlPGE0Nsy7hlebS4liisXOrN3jFz asKyUws3VXek4V65lHwB23BVzsnFMn/bw/rPliqXGcwl8CoJu8dSyrCcd1Ibs0/Inq9S9+t0 VmWiQWfQkz4rvEeTQkp/VfgZ6z98JRW7S6l6eophoWs0/ZyRfOm+QVSqRfFZdxdP2PlGeIFM C3fXJgygXJkFPyWkVElr76JTbtSHsGWbt6xUlYHKXWo+xf9WgtLeby3cfSkEchACrxDrQpj+ Jt/JFP+q997dybkyZ5IoHWuPkn7uZGBrKIHmBunTco1+cKSuRiSCYpBIXZMHCzPgVDjk4viP brV9NwRkmaOxVvye0vctJeWvJ6KA7NoAURplIGCqkCRwg0MmLrfoZnK/gRqVJ/f6adhU1oo6 z4p2/z3PemA0C0ANatgHgBb90cd16AUxpdEQmOCmdNnNJF/3Zt3inzF+NFzHoM5Vwq6rc1JP jfC3oqRLJzqAEHBDjQFlqNR3IFCIAo4SYQRBdAHBCzkM4rWyRhuVABEBAAHCwV8EGAECAAkF AlYFJhkCGwwACgkQ8ww4vT8vvjwg9w//VQrcnVg3TsjEybxDEUBm8dBmnKqcnTBFmxN5FFtI WlEuY8+YMiWRykd8Ln9RJ/98/ghABHz9TN8TRo2b6WimV64FmlVn17Ri6FgFU3xNt9TTEChq AcNg88eYryKsYpFwegGpwUlaUaaGh1m9OrTzcQy+klVfZWaVJ9Nw0keoGRGb8j4XjVpL8+2x OhXKrM1fzzb8JtAuSbuzZSQPDwQEI5CKKxp7zf76J21YeRrEW4WDznPyVcDTa+tz++q2S/Bp P4W98bXCBIuQgs2m+OflERv5c3Ojldp04/S4NEjXEYRWdiCxN7ca5iPml5gLtuvhJMSy36gl U6IW9kn30IWuSoBpTkgV7rLUEhh9Ms82VWW/h2TxL8enfx40PrfbDtWwqRID3WY8jLrjKfTd R3LW8BnUDNkG+c4FzvvGUs8AvuqxxyHbXAfDx9o/jXfPHVRmJVhSmd+hC3mcQ+4iX5bBPBPM oDqSoLt5w9GoQQ6gDVP2ZjTWqwSRMLzNr37rJjZ1pt0DCMMTbiYIUcrhX8eveCJtY7NGWNyx FCRkhxRuGcpwPmRVDwOl39MB3iTsRighiMnijkbLXiKoJ5CDVvX5yicNqYJPKh5MFXN1bvsB kmYiStMRbrD0HoY1kx5/VozBtc70OU0EB8Wrv9hZD+Ofp0T3KOr1RUHvCZoLURfFhSQ= In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -q2nyiBvMOVYInF9OmM1x9VL4rQqikFHhQ7hl1waHxg_1779288758 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: 3NONGQFQXZA45GGALK5UZOLHAXFGBGPX X-Message-ID-Hash: 3NONGQFQXZA45GGALK5UZOLHAXFGBGPX X-MailFrom: lvivier@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 5/11/26 12:52, David Gibson wrote: > On Thu, Apr 16, 2026 at 06:16:18PM +0200, Laurent Vivier wrote: >> Build the Ethernet, IP, and TCP headers on the stack instead of >> directly in the buffer via pointer casts, then write them into the >> iovec with IOV_PUSH_HEADER(). This mirrors the approach already used >> in tcp_vu_prepare() and udp_vu_prepare(). >> >> Remove the vu_eth(), vu_ip(), vu_payloadv4() and vu_payloadv6() helpers >> from vu_common.h, as they are no longer used anywhere. >> >> Introduce tcp_vu_send_dup() to handle DUP_ACK duplication using >> vu_collect() and iov_memcopy() instead of a plain memcpy(), so that > > s/iov_memcopy/iov_memcpy/ > >> the duplicated frame is also properly scattered across multiple iovecs. >> >> Signed-off-by: Laurent Vivier >> --- >> iov.c | 1 - >> tcp_vu.c | 153 ++++++++++++++++++++++++++++++---------------------- >> vu_common.h | 20 ------- >> 3 files changed, 90 insertions(+), 84 deletions(-) >> >> diff --git a/iov.c b/iov.c >> index c0d9c6d21322..31fc3e479572 100644 >> --- a/iov.c >> +++ b/iov.c >> @@ -208,7 +208,6 @@ void iov_memset(const struct iovec *iov, size_t iov_cnt, size_t offset, int c, >> * >> * Return: total number of bytes copied >> */ >> -/* cppcheck-suppress unusedFunction */ >> size_t iov_memcpy(struct iovec *dst_iov, size_t dst_iov_cnt, size_t dst_offset, >> const struct iovec *src_iov, size_t src_iov_cnt, >> size_t src_offset, size_t length) >> diff --git a/tcp_vu.c b/tcp_vu.c >> index 96b16007701d..7f7e43860b10 100644 >> --- a/tcp_vu.c >> +++ b/tcp_vu.c >> @@ -74,6 +74,42 @@ static size_t tcp_vu_hdrlen(bool v6) >> return hdrlen; >> } >> >> +/** >> + * tcp_vu_send_dup() - Duplicate a frame into a new virtqueue element >> + * @c: Execution context >> + * @vq: Receive virtqueue >> + * @dest_elem: Destination virtqueue element to collect >> + * @dest_iov: Destination iovec array for collected buffers >> + * @max_dest_iov: Maximum number of entries in @dest_iov >> + * @src_iov: Source iovec array containing the frame to duplicate >> + * @src_cnt: Number of entries in @src_iov > > As Jon noted, @vnlen is missing. > >> + * >> + * Return: number of virtqueue elements collected (0 if none available) >> + */ >> +static int tcp_vu_send_dup(const struct ctx *c, struct vu_virtq *vq, >> + struct vu_virtq_element *dest_elem, >> + struct iovec *dest_iov, size_t max_dest_iov, >> + const struct iovec *src_iov, size_t src_cnt, >> + size_t vnlen) >> +{ >> + const struct vu_dev *vdev = c->vdev; >> + size_t dest_cnt; >> + int elem_cnt; >> + >> + elem_cnt = vu_collect(vdev, vq, dest_elem, 1, dest_iov, max_dest_iov, >> + &dest_cnt, vnlen, NULL); >> + if (elem_cnt == 0) >> + return 0; >> + >> + iov_memcpy(dest_iov, dest_cnt, 0, src_iov, src_cnt, 0, >> + MAX(VNET_HLEN + ETH_ZLEN, vnlen)); >> + >> + if (*c->pcap) >> + pcap_iov(dest_iov, dest_cnt, VNET_HLEN, vnlen - VNET_HLEN); >> + >> + return elem_cnt; >> +} >> + >> /** >> * tcp_vu_send_flag() - Send segment with flags to vhost-user (no payload) >> * @c: Execution context >> @@ -86,97 +122,88 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) >> { >> struct vu_dev *vdev = c->vdev; >> struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; >> + size_t optlen, hdrlen, iov_cnt, iov_used; >> struct vu_virtq_element flags_elem[2]; > > Does the rationale for this having only 2 elements still apply? Yes, this is element, not iovec. One for the flags, an other one for the DUP. > >> - size_t optlen, hdrlen, l2len; >> - struct ipv6hdr *ip6h = NULL; >> - struct iphdr *ip4h = NULL; >> - struct iovec flags_iov[2]; >> - struct tcp_syn_opts *opts; >> + struct iovec flags_iov[64]; >> + int elem_cnt, dup_elem_cnt = 0; >> + struct tcp_syn_opts opts; >> struct iov_tail payload; >> - struct tcphdr *th; >> - struct ethhdr *eh; >> + struct ipv6hdr ip6h; >> + struct iphdr ip4h; >> + struct tcphdr th; >> + struct ethhdr eh; >> uint32_t seq; >> - int elem_cnt; >> int ret; >> >> hdrlen = tcp_vu_hdrlen(CONN_V6(conn)); >> >> elem_cnt = vu_collect(vdev, vq, &flags_elem[0], 1, >> - &flags_iov[0], 1, NULL, >> - hdrlen + sizeof(*opts), NULL); >> - if (elem_cnt != 1) >> + flags_iov, ARRAY_SIZE(flags_iov), &iov_cnt, >> + hdrlen + sizeof(opts), NULL); >> + if (elem_cnt == 0) >> return -1; >> >> - assert(flags_elem[0].in_num == 1); >> - assert(flags_elem[0].in_sg[0].iov_len >= >> - MAX(hdrlen + sizeof(*opts), ETH_ZLEN + VNET_HLEN)); >> - >> - eh = vu_eth(flags_elem[0].in_sg[0].iov_base); >> - >> - memcpy(eh->h_dest, c->guest_mac, sizeof(eh->h_dest)); >> - memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source)); >> - >> - if (CONN_V4(conn)) { >> - eh->h_proto = htons(ETH_P_IP); >> - >> - ip4h = vu_ip(flags_elem[0].in_sg[0].iov_base); >> - *ip4h = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP); >> - >> - th = vu_payloadv4(flags_elem[0].in_sg[0].iov_base); >> - } else { >> - eh->h_proto = htons(ETH_P_IPV6); >> + memcpy(eh.h_dest, c->guest_mac, sizeof(eh.h_dest)); >> >> - ip6h = vu_ip(flags_elem[0].in_sg[0].iov_base); >> - *ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP); >> - th = vu_payloadv6(flags_elem[0].in_sg[0].iov_base); >> - } >> + if (CONN_V4(conn)) >> + ip4h = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP); >> + else >> + ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP); >> >> - memset(th, 0, sizeof(*th)); >> - th->doff = sizeof(*th) / 4; >> - th->ack = 1; > > Where are doff and ack now initialised? Or were these already unneeded? They are set in tcp_prepare_flags(). Thanks, Laurent