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[176.103.220.4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4398a292babsm2455923f8f.37.2026.02.24.03.56.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Feb 2026 03:56:52 -0800 (PST) From: Stefano Brivio To: Laurent Vivier Subject: Re: [PATCH v2 1/2] tcp_vu: vu_pad() expects l2 length Message-ID: <20260224125645.67d3e81d@elisabeth> In-Reply-To: <20260223141027.2205762-2-lvivier@redhat.com> References: <20260223141027.2205762-1-lvivier@redhat.com> <20260223141027.2205762-2-lvivier@redhat.com> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) MIME-Version: 1.0 Date: Tue, 24 Feb 2026 12:56:52 +0100 (CET) X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: eYCR1QUGHjjjA3I8GC9nbuEqyCNLy2P0BX7Hrejx-yA_1771934215 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: HHD5C55QNMQ6H7K25KTZAFXGOOTPCNKM X-Message-ID-Hash: HHD5C55QNMQ6H7K25KTZAFXGOOTPCNKM X-MailFrom: sbrivio@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 Mon, 23 Feb 2026 15:10:26 +0100 Laurent Vivier wrote: > tcp_vu_hdrlen() returns a length that includes VNET_HLEN (the virtio > net header), No need for this patch/series but: /** * tcp_vu_hdrlen() - return the size of the header in level 2 frame (TCP) * @v6: Set for IPv6 packet * * Return: return the size of the header */ ...can you fix that at some point? :) It's really not clear what it returns. I assumed "level 2" meant Layer-2 length (802.3-like), without virtio-net stuff, hence this issue. > but vu_pad() expects the Layer-2 frame length, which > should not include the virtio header. Passing the inflated length > means short frames aren't padded to the minimum 60-byte Ethernet > frame size (ETH_ZLEN). > > Subtract VNET_HLEN from hdrlen when computing the l2 length passed > to vu_pad() in both tcp_vu_send_flag() and tcp_vu_data_from_sock(). > > Fixes: 0cb8f9003654 ("tcp, udp: Pad batched frames for vhost-user modes to 60 bytes (802.3 minimum)") > Signed-off-by: Laurent Vivier > --- > tcp_vu.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/tcp_vu.c b/tcp_vu.c > index 3847a4e92087..2c9ddba0c9a4 100644 > --- a/tcp_vu.c > +++ b/tcp_vu.c > @@ -71,8 +71,8 @@ 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; > struct vu_virtq_element flags_elem[2]; > + size_t optlen, hdrlen, l2len; > struct ipv6hdr *ip6h = NULL; > struct iphdr *ip4h = NULL; > struct iovec flags_iov[2]; > @@ -137,7 +137,8 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) > tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &payload, > NULL, seq, !*c->pcap); > > - vu_pad(&flags_elem[0].in_sg[0], hdrlen + optlen); > + l2len = optlen + hdrlen - VNET_HLEN; > + vu_pad(&flags_elem[0].in_sg[0], l2len); > > if (*c->pcap) > pcap_iov(&flags_elem[0].in_sg[0], 1, VNET_HLEN); > @@ -446,6 +447,7 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn) > int buf_cnt = head[i + 1] - head[i]; > ssize_t dlen = iov_size(iov, buf_cnt) - hdrlen; > bool push = i == head_cnt - 1; > + size_t l2len; > > vu_set_vnethdr(vdev, iov->iov_base, buf_cnt); > > @@ -457,7 +459,8 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn) > tcp_vu_prepare(c, conn, iov, buf_cnt, &check, !*c->pcap, push); > > /* Pad first/single buffer only, it's at least ETH_ZLEN long */ > - vu_pad(iov, dlen + hdrlen); > + l2len = dlen + hdrlen - VNET_HLEN; > + vu_pad(iov, l2len); > > if (*c->pcap) > pcap_iov(iov, buf_cnt, VNET_HLEN); -- Stefano