On Sat, Feb 17, 2024 at 04:07:17PM +0100, Laurent Vivier wrote:Introduce functions to copy to/from a buffer from/to an iovec array, to compute data length in in bytes of an iovec and to copy memory from an iovec to another. iov_from_buf(), iov_to_buf(), iov_size(), iov_copy(). Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>--- Notes: v3: - update copyright statement (but keep it as proposed by Stefano) - open code of iov_fill_from_buf()/iov_fill_to_buf() into iov_frombuf()/iov_to_buf() - coding style cleanup - use size_t for the length of the vectors v2: - reorder added files in alphanetical order in Makefile - update comments, cosmetic cleanup - rename iov_from_buf_full/iov_to_buf_full to iov_fill_from_buf/iov_fill_to_buf - split loops that manage offset and bytes copy. - move iov_from_buf()/iov_to_buf() to iov.c Makefile | 8 +-- iov.c | 171 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ iov.h | 29 ++++++++++ 3 files changed, 204 insertions(+), 4 deletions(-) create mode 100644 iov.c create mode 100644 iov.h diff --git a/Makefile b/Makefile index af4fa87e7e13..156398b3844e 100644 --- a/Makefile +++ b/Makefile @@ -45,16 +45,16 @@ FLAGS += -DVERSION=\"$(VERSION)\" FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS) PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c flow.c icmp.c \ - igmp.c isolation.c lineread.c log.c mld.c ndp.c netlink.c packet.c \ - passt.c pasta.c pcap.c pif.c port_fwd.c tap.c tcp.c tcp_splice.c udp.c \ - util.c + igmp.c iov.c isolation.c lineread.c log.c mld.c ndp.c netlink.c \ + packet.c passt.c pasta.c pcap.c pif.c port_fwd.c tap.c tcp.c \ + tcp_splice.c udp.c util.c QRAP_SRCS = qrap.c SRCS = $(PASST_SRCS) $(QRAP_SRCS) MANPAGES = passt.1 pasta.1 qrap.1 PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h flow.h \ - flow_table.h icmp.h inany.h isolation.h lineread.h log.h ndp.h \ + flow_table.h icmp.h inany.h iov.h isolation.h lineread.h log.h ndp.h \ netlink.h packet.h passt.h pasta.h pcap.h pif.h port_fwd.h siphash.h \ tap.h tcp.h tcp_conn.h tcp_splice.h udp.h util.h HEADERS = $(PASST_HEADERS) seccomp.h diff --git a/iov.c b/iov.c new file mode 100644 index 000000000000..1135f87e2f45 --- /dev/null +++ b/iov.c @@ -0,0 +1,171 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * iov.h - helpers for using (partial) iovecs. + * + * Copyright Red Hat + * Author: Laurent Vivier <lvivier(a)redhat.com> + * + * This file also contains code originally from QEMU include/qemu/iov.h + * and licensed under the following terms: + * + * Copyright (C) 2010 Red Hat, Inc. + * + * Author(s): + * Amit Shah <amit.shah(a)redhat.com> + * Michael Tokarev <mjt(a)tls.msk.ru> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + * + * Contributions after 2012-01-13 are licensed under the terms of the + * GNU GPL, version 2 or (at your option) any later version. + */ +#include <sys/socket.h> + +#include "util.h" +#include "iov.h" + +/** + * iov_from_buf - Copy data from a buffer to an I/O vector (struct iovec) + * efficiently. + * + * @iov: Pointer to the array of struct iovec describing the + * scatter/gather I/O vector. + * @iov_cnt: Number of elements in the iov array. + * @offset: Byte offset in the iov array where copying should start. + * @buf: Pointer to the source buffer containing the data to copy. + * @bytes: Total number of bytes to copy from buf to iov. + * + * Returns: The number of bytes successfully copied. + */ +size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt, + size_t offset, const void *buf, size_t bytes) +{ + unsigned int i; + size_t copied; + + if (__builtin_constant_p(bytes) && iov_cnt && + offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) { + memcpy((char *)iov[0].iov_base + offset, buf, bytes); + return bytes; + } + + /* skipping offset bytes in the iovec */ + for (i = 0; offset >= iov[i].iov_len && i < iov_cnt; i++) + offset -= iov[i].iov_len; + + /* copying data */ + for (copied = 0; copied < bytes && i < iov_cnt; i++) { + size_t len = MIN(iov[i].iov_len - offset, bytes - copied); + + memcpy((char *)iov[i].iov_base + offset, (char *)buf + copied, + len); + copied += len; + offset = 0; + } + + return copied; +} + +/** + * iov_to_buf - Copy data from a scatter/gather I/O vector (struct iovec) to + * a buffer efficiently. + * + * @iov: Pointer to the array of struct iovec describing the scatter/gather + * I/O vector. + * @iov_cnt: Number of elements in the iov array. + * @offset: Offset within the first element of iov from where copying should start. + * @buf: Pointer to the destination buffer where data will be copied. + * @bytes: Total number of bytes to copy from iov to buf. + * + * Returns: The number of bytes successfully copied. + */ +size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt, + size_t offset, void *buf, size_t bytes) +{ + unsigned int i; + size_t copied; + + if (__builtin_constant_p(bytes) && iov_cnt && + offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) { + memcpy(buf, (char *)iov[0].iov_base + offset, bytes); + return bytes; + } + + /* skipping offset bytes in the iovec */ + for (i = 0; offset >= iov[i].iov_len && i < iov_cnt; i++) + offset -= iov[i].iov_len; + + /* copying data */ + for (copied = 0; copied < bytes && i < iov_cnt; i++) { + size_t len = MIN(iov[i].iov_len - offset, bytes - copied); + memcpy((char *)buf + copied, (char *)iov[i].iov_base + offset, + len); + copied += len; + offset = 0; + } + + return copied; +} + +/** + * iov_size - Calculate the total size of a scatter/gather I/O vector + * (struct iovec). + * + * @iov: Pointer to the array of struct iovec describing the + * scatter/gather I/O vector. + * @iov_cnt: Number of elements in the iov array. + * + * Returns: The total size in bytes. + */ +size_t iov_size(const struct iovec *iov, size_t iov_cnt) +{ + unsigned int i; + size_t len; + + for (i = 0, len = 0; i < iov_cnt; i++) + len += iov[i].iov_len; + + return len; +} + +/** + * iov_copy - Copy data from one scatter/gather I/O vector (struct iovec) to + * another. + * + * @dst_iov: Pointer to the destination array of struct iovec describing + * the scatter/gather I/O vector to copy to. + * @dst_iov_cnt: Number of elements in the destination iov array. + * @iov: Pointer to the source array of struct iovec describing + * the scatter/gather I/O vector to copy from. + * @iov_cnt: Number of elements in the source iov array. + * @offset: Offset within the source iov from where copying should start. + * @bytes: Total number of bytes to copy from iov to dst_iov. + * + * Returns: The number of elements successfully copied to the destination + * iov array. + */ +unsigned iov_copy(struct iovec *dst_iov, size_t dst_iov_cnt, + const struct iovec *iov, size_t iov_cnt, + size_t offset, size_t bytes) +{ + unsigned int i, j; + size_t len; + + /* skipping offset bytes in the iovec */ + for (i = 0; offset >= iov[i].iov_len && i < iov_cnt; i++) + offset -= iov[i].iov_len; + + /* copying data */ + for (j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) { + len = MIN(bytes, iov[i].iov_len - offset); + + dst_iov[j].iov_base = (char *)iov[i].iov_base + offset; + dst_iov[j].iov_len = len; + j++; + bytes -= len; + offset = 0; + } + + return j; +} diff --git a/iov.h b/iov.h new file mode 100644 index 000000000000..ee35a75d0870 --- /dev/null +++ b/iov.h @@ -0,0 +1,29 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * iov.c - helpers for using (partial) iovecs. + * + * Copyrigh Red Hat + * Author: Laurent Vivier <lvivier(a)redhat.com> + * + * This file also contains code originally from QEMU include/qemu/iov.h: + * + * Author(s): + * Amit Shah <amit.shah(a)redhat.com> + * Michael Tokarev <mjt(a)tls.msk.ru> + */ + +#ifndef IOVEC_H +#define IOVEC_H + +#include <unistd.h> +#include <string.h> + +size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt, + size_t offset, const void *buf, size_t bytes); +size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt, + size_t offset, void *buf, size_t bytes); +size_t iov_size(const struct iovec *iov, size_t iov_cnt); +unsigned iov_copy(struct iovec *dst_iov, size_t dst_iov_cnt, + const struct iovec *iov, size_t iov_cnt, + size_t offset, size_t bytes); +#endif /* IOVEC_H */-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson