From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by passt.top (Postfix) with ESMTPS id 5E17B5A026E for ; Mon, 5 Dec 2022 09:14:35 +0100 (CET) Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4NQbtY2VXSz4xP3; Mon, 5 Dec 2022 19:14:29 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=201602; t=1670228069; bh=HcVw+akX1Vt4gu3FF3J5ATo4X07kWineqLLkl3z982E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S6fiafU27JIZdx/ZvFzwPX1TqZqVqa8c9BqnIufVtU5uxU0afY6c4doo9HPyQ1tqs rGvhcBzSqLI2rJ7RyEmyr3rjvXrup5IJ9AqX142ircpulpN4act/dHr8OGnAmXYkxF O3gJRYVE2MWSncl5lbN5oBE9DHDL72+fxiw+Xk4k= From: David Gibson To: Stefano Brivio , passt-dev@passt.top Subject: [PATCH 1/8] udp: Move sending pasta tap frames to the end of udp_sock_handler() Date: Mon, 5 Dec 2022 19:14:18 +1100 Message-Id: <20221205081425.2614425-2-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221205081425.2614425-1-david@gibson.dropbear.id.au> References: <20221205081425.2614425-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: XOZNE3WSNQQJ2ME63HKXNGA34SCUHEYZ X-Message-ID-Hash: XOZNE3WSNQQJ2ME63HKXNGA34SCUHEYZ X-MailFrom: dgibson@gandalf.ozlabs.org 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: David Gibson X-Mailman-Version: 3.3.3 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: udp_sock_handler() has a surprising difference in flow between pasta and passt mode: For pasta we send each frame to the tap interface as we prepare it. For passt, though, we prepare all the frames, then send them with a single sendmmsg(). Alter the pasta path to also prepare all the frames, then send them at the end. We already have a suitable data structure for the passt case. This will make it easier to abstract out the tap backend difference in future. Signed-off-by: David Gibson --- udp.c | 61 ++++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 42 insertions(+), 19 deletions(-) diff --git a/udp.c b/udp.c index 4610a02..a27fe88 100644 --- a/udp.c +++ b/udp.c @@ -783,6 +783,35 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport, return buf_len; } +/** + * udp_tap_send_pasta() - Send datagrams to the pasta tap interface + * @c: Execution context + * @mmh: Array of message headers to send + * @n: Number of message headers to send + * + * #syscalls:pasta write + */ +static void udp_tap_send_pasta(const struct ctx *c, struct mmsghdr *mmh, + unsigned int n) +{ + unsigned int i, j; + + for (i = 0; i < n; i++) { + for (j = 0; j < mmh[i].msg_hdr.msg_iovlen; j++) { + struct iovec *iov = &mmh[i].msg_hdr.msg_iov[j]; + + /* We can't use writev() because the tap + * character device relies on the write() + * boundaries to discern frame boundaries + */ + if (write(c->fd_tap, iov->iov_base, iov->iov_len) < 0) + debug("tap write: %s", strerror(errno)); + else + pcap(iov->iov_base, iov->iov_len); + } + } +} + /** * udp_sock_handler() - Handle new data from socket * @c: Execution context @@ -835,31 +864,25 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events, else buf_len = udp_update_hdr4(c, i, dstport, now); - if (c->mode == MODE_PASTA) { - void *frame = tap_iov[i].iov_base; + tap_iov[i].iov_len = buf_len; - if (write(c->fd_tap, frame, buf_len) < 0) - debug("tap write: %s", strerror(errno)); - pcap(frame, buf_len); - } else { - tap_iov[i].iov_len = buf_len; - - /* With bigger messages, qemu closes the connection. */ - if (msg_bufs && msg_len + buf_len > SHRT_MAX) { - tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs; - msg_i++; - tap_mmh[msg_i].msg_hdr.msg_iov = &tap_iov[i]; - msg_len = msg_bufs = 0; - } - - msg_len += buf_len; - msg_bufs++; + /* With bigger messages, qemu closes the connection. */ + if (c->mode == MODE_PASST && msg_bufs && + msg_len + buf_len > SHRT_MAX) { + tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs; + msg_i++; + tap_mmh[msg_i].msg_hdr.msg_iov = &tap_iov[i]; + msg_len = msg_bufs = 0; } + msg_len += buf_len; + msg_bufs++; } tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs; - if (c->mode == MODE_PASTA) + if (c->mode == MODE_PASTA) { + udp_tap_send_pasta(c, tap_mmh, msg_i + 1); return; + } ret = sendmmsg(c->fd_tap, tap_mmh, msg_i + 1, MSG_NOSIGNAL | MSG_DONTWAIT); -- 2.38.1