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08ea3cc581
At the moment these take separate pointers to the tap specific and IP headers, but expect the TCP header and payload as a single tcp_payload_t. As well as being slightly inconsistent, this involves some slightly iffy pointer shenanigans when called on the flags path with a tcp_flags_t instead of a tcp_payload_t. More importantly, it's inconvenient for the upcoming vhost-user case, where the TCP header and payload might not be contiguous. Furthermore, the payload itself might not be contiguous. So, pass the TCP header as its own pointer, and the TCP payload as an IO vector. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
249 lines
6.9 KiB
C
249 lines
6.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* iov.h - helpers for using (partial) iovecs.
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*
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* Copyright Red Hat
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* Author: Laurent Vivier <lvivier@redhat.com>
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*
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* This file also contains code originally from QEMU include/qemu/iov.h
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* and licensed under the following terms:
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*
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* Copyright (C) 2010 Red Hat, Inc.
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*
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* Author(s):
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* Amit Shah <amit.shah@redhat.com>
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* Michael Tokarev <mjt@tls.msk.ru>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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* Contributions after 2012-01-13 are licensed under the terms of the
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* GNU GPL, version 2 or (at your option) any later version.
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*/
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#include <sys/socket.h>
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#include "util.h"
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#include "iov.h"
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/* iov_skip_bytes() - Skip leading bytes of an IO vector
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* @iov: IO vector
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* @n: Number of entries in @iov
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* @skip: Number of leading bytes of @iov to skip
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* @offset: Offset of first unskipped byte in its @iov entry
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*
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* Return: index I of individual struct iovec which contains the byte at @skip
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* bytes into the vector (as though all its buffers were contiguous).
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* If @offset is non-NULL, update it to the offset of that byte within
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* @iov[I] (guaranteed to be less than @iov[I].iov_len) If the whole
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* vector has <= @skip bytes, return @n.
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*/
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size_t iov_skip_bytes(const struct iovec *iov, size_t n,
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size_t skip, size_t *offset)
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{
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size_t off = skip, i;
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for (i = 0; i < n; i++) {
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if (off < iov[i].iov_len)
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break;
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off -= iov[i].iov_len;
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}
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if (offset)
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*offset = off;
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return i;
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}
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/**
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* iov_from_buf - Copy data from a buffer to an I/O vector (struct iovec)
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* efficiently.
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*
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* @iov: Pointer to the array of struct iovec describing the
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* scatter/gather I/O vector.
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* @iov_cnt: Number of elements in the iov array.
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* @offset: Byte offset in the iov array where copying should start.
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* @buf: Pointer to the source buffer containing the data to copy.
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* @bytes: Total number of bytes to copy from buf to iov.
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*
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* Returns: The number of bytes successfully copied.
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*/
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size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt,
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size_t offset, const void *buf, size_t bytes)
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{
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unsigned int i;
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size_t copied;
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if (__builtin_constant_p(bytes) && iov_cnt &&
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offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
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memcpy((char *)iov[0].iov_base + offset, buf, bytes);
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return bytes;
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}
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i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
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/* copying data */
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for (copied = 0; copied < bytes && i < iov_cnt; i++) {
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size_t len = MIN(iov[i].iov_len - offset, bytes - copied);
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memcpy((char *)iov[i].iov_base + offset, (char *)buf + copied,
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len);
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copied += len;
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offset = 0;
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}
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return copied;
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}
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/**
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* iov_to_buf - Copy data from a scatter/gather I/O vector (struct iovec) to
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* a buffer efficiently.
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*
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* @iov: Pointer to the array of struct iovec describing the scatter/gather
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* I/O vector.
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* @iov_cnt: Number of elements in the iov array.
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* @offset: Offset within the first element of iov from where copying should start.
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* @buf: Pointer to the destination buffer where data will be copied.
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* @bytes: Total number of bytes to copy from iov to buf.
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*
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* Returns: The number of bytes successfully copied.
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*/
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/* cppcheck-suppress unusedFunction */
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size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt,
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size_t offset, void *buf, size_t bytes)
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{
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unsigned int i;
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size_t copied;
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if (__builtin_constant_p(bytes) && iov_cnt &&
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offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
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memcpy(buf, (char *)iov[0].iov_base + offset, bytes);
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return bytes;
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}
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i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
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/* copying data */
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for (copied = 0; copied < bytes && i < iov_cnt; i++) {
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size_t len = MIN(iov[i].iov_len - offset, bytes - copied);
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memcpy((char *)buf + copied, (char *)iov[i].iov_base + offset,
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len);
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copied += len;
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offset = 0;
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}
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return copied;
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}
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/**
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* iov_size - Calculate the total size of a scatter/gather I/O vector
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* (struct iovec).
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*
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* @iov: Pointer to the array of struct iovec describing the
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* scatter/gather I/O vector.
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* @iov_cnt: Number of elements in the iov array.
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*
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* Returns: The total size in bytes.
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*/
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size_t iov_size(const struct iovec *iov, size_t iov_cnt)
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{
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unsigned int i;
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size_t len;
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for (i = 0, len = 0; i < iov_cnt; i++)
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len += iov[i].iov_len;
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return len;
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}
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/**
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* iov_tail_prune() - Remove any unneeded buffers from an IOV tail
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* @tail: IO vector tail (modified)
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*
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* If an IOV tail's offset is large enough, it may not include any bytes from
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* the first (or first several) buffers in the underlying IO vector. Modify the
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* tail's representation so it contains the same logical bytes, but only
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* includes buffers that are actually needed. This will avoid stepping through
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* unnecessary elements of the underlying IO vector on future operations.
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*
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* Return: true if the tail still contains any bytes, otherwise false
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*/
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bool iov_tail_prune(struct iov_tail *tail)
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{
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size_t i;
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i = iov_skip_bytes(tail->iov, tail->cnt, tail->off, &tail->off);
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tail->iov += i;
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tail->cnt -= i;
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return !!tail->cnt;
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}
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/**
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* iov_tail_size - Calculate the total size of an IO vector tail
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* @tail: IO vector tail
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*
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* Returns: The total size in bytes.
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*/
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size_t iov_tail_size(struct iov_tail *tail)
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{
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iov_tail_prune(tail);
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return iov_size(tail->iov, tail->cnt) - tail->off;
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}
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/**
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* iov_peek_header_() - Get pointer to a header from an IOV tail
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* @tail: IOV tail to get header from
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* @len: Length of header to get, in bytes
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* @align: Required alignment of header, in bytes
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*
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* @tail may be pruned, but will represent the same bytes as before.
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*
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* Returns: Pointer to the first @len logical bytes of the tail, NULL if that
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* overruns the IO vector, is not contiguous or doesn't have the
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* requested alignment.
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*/
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void *iov_peek_header_(struct iov_tail *tail, size_t len, size_t align)
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{
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char *p;
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if (!iov_tail_prune(tail))
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return NULL; /* Nothing left */
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if (tail->off + len < tail->off)
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return NULL; /* Overflow */
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if (tail->off + len > tail->iov[0].iov_len)
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return NULL; /* Not contiguous */
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p = (char *)tail->iov[0].iov_base + tail->off;
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if ((uintptr_t)p % align)
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return NULL; /* not aligned */
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return p;
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}
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/**
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* iov_remove_header_() - Remove a header from an IOV tail
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* @tail: IOV tail to remove header from (modified)
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* @len: Length of header to remove, in bytes
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* @align: Required alignment of header, in bytes
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*
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* On success, @tail is updated so that it longer includes the bytes of the
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* returned header.
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*
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* Returns: Pointer to the first @len logical bytes of the tail, NULL if that
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* overruns the IO vector, is not contiguous or doesn't have the
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* requested alignment.
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*/
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void *iov_remove_header_(struct iov_tail *tail, size_t len, size_t align)
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{
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char *p = iov_peek_header_(tail, len, align);
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if (!p)
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return NULL;
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tail->off = tail->off + len;
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return p;
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}
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