f92bb8c19a
This patch adds a new netbe_peek_recvlen() function to the net backend API. The new function allows the virtio-net receive code to know in advance how many virtio descriptors chains will be needed to receive the next packet. As a result, the implementation of the virtio-net mergeable rx buffers feature becomes efficient, so that we can enable it also with the tap(4) backend. For the tap(4) backend, a bounce buffer is introduced to implement the peeck_recvlen() callback, which implies an additional packet copy on the receive datapath. In the future, it should be possible to remove the bounce buffer (and so the additional copy), by obtaining the length of the next packet from kevent data. Reviewed by: grehan, aleksandr.fedorov@itglobal.com MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D23472
150 lines
3.5 KiB
C
150 lines
3.5 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 2016 Jakub Klama <jceel@FreeBSD.org>.
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* Copyright (c) 2018 Alexander Motin <mav@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer
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* in this position and unchanged.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/uio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "iov.h"
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void
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seek_iov(const struct iovec *iov1, int niov1, struct iovec *iov2, int *niov2,
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size_t seek)
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{
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size_t remainder = 0;
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size_t left = seek;
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int i, j;
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for (i = 0; i < niov1; i++) {
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size_t toseek = MIN(left, iov1[i].iov_len);
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left -= toseek;
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if (toseek == iov1[i].iov_len)
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continue;
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if (left == 0) {
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remainder = toseek;
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break;
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}
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}
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for (j = i; j < niov1; j++) {
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iov2[j - i].iov_base = (char *)iov1[j].iov_base + remainder;
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iov2[j - i].iov_len = iov1[j].iov_len - remainder;
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remainder = 0;
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}
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*niov2 = j - i;
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}
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size_t
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count_iov(const struct iovec *iov, int niov)
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{
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size_t total = 0;
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int i;
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for (i = 0; i < niov; i++)
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total += iov[i].iov_len;
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return (total);
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}
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void
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truncate_iov(struct iovec *iov, int *niov, size_t length)
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{
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size_t done = 0;
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int i;
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for (i = 0; i < *niov; i++) {
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size_t toseek = MIN(length - done, iov[i].iov_len);
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done += toseek;
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if (toseek <= iov[i].iov_len) {
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iov[i].iov_len = toseek;
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*niov = i + 1;
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return;
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}
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}
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}
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ssize_t
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iov_to_buf(const struct iovec *iov, int niov, void **buf)
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{
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size_t ptr, total;
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int i;
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total = count_iov(iov, niov);
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*buf = realloc(*buf, total);
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if (*buf == NULL)
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return (-1);
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for (i = 0, ptr = 0; i < niov; i++) {
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memcpy(*buf + ptr, iov[i].iov_base, iov[i].iov_len);
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ptr += iov[i].iov_len;
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}
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return (total);
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}
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ssize_t
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buf_to_iov(const void *buf, size_t buflen, const struct iovec *iov, int niov,
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size_t seek)
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{
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struct iovec *diov;
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size_t off = 0, len;
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int i;
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if (seek > 0) {
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int ndiov;
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diov = malloc(sizeof(struct iovec) * niov);
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seek_iov(iov, niov, diov, &ndiov, seek);
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iov = diov;
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niov = ndiov;
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}
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for (i = 0; i < niov && off < buflen; i++) {
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len = MIN(iov[i].iov_len, buflen - off);
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memcpy(iov[i].iov_base, buf + off, len);
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off += len;
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}
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if (seek > 0)
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free(diov);
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return ((ssize_t)off);
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}
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