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/* $OpenBSD: cmsgsize.c,v 1.3 2020/01/22 07:52:37 deraadt Exp $ */
/*
* Copyright (c) 2017 Alexander Markert <alexander.markert@siemens.com>
* Copyright (c) 2018 Alexander Bluhm <bluhm@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define CFG_PORT 5000
#define CFG_SO_MAX_SEND_BUFFER 1024
char payload[CFG_SO_MAX_SEND_BUFFER];
int test_cmsgsize(int, struct in_addr *, struct in_addr *,
unsigned int, unsigned int);
int
main(int argc, char *argv[])
{
int so, bytes;
struct in_addr src, dst;
if (argc != 3)
errx(2, "usage: %s <source_address> <destination_address>",
argv[0]);
if (inet_pton(AF_INET, argv[1], &src) != 1)
err(1, "unable to parse source address");
if (inet_pton(AF_INET, argv[2], &dst) != 1)
err(1, "unable to parse destination address");
/* 1: !blocking, cmsg + payload > sndbufsize => EMSGSIZE */
so = socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK, IPPROTO_UDP);
if (so < 0)
err(1, "1: socket");
bytes = test_cmsgsize(so, &src, &dst, CFG_SO_MAX_SEND_BUFFER,
CFG_SO_MAX_SEND_BUFFER);
if (bytes >= 0)
errx(1, "1: %d bytes sent\n", bytes);
if (errno != EMSGSIZE)
err(-1, "1: incorrect errno");
close(so);
/* 2: blocking, cmsg + payload > sndbufsize => EMSGSIZE */
so = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (so < 0)
err(1, "2: socket");
bytes = test_cmsgsize(so, &src, &dst, CFG_SO_MAX_SEND_BUFFER,
CFG_SO_MAX_SEND_BUFFER);
if (bytes >= 0)
errx(1, "2: %d bytes sent\n", bytes);
if (errno != EMSGSIZE)
err(-1, "2: incorrect errno");
close(so);
/* 3: !blocking, cmsg + payload < sndbufsize => OK */
so = socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK, IPPROTO_UDP);
if (so < 0)
err(1, "3: socket 3");
bytes = test_cmsgsize(so, &src, &dst, CFG_SO_MAX_SEND_BUFFER,
CFG_SO_MAX_SEND_BUFFER/2);
if (bytes < 0)
err(1, "3: got errno");
close(so);
/* 4: blocking, cmsg + payload < sndbufsize => OK */
so = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (so < 0)
err(1, "4: socket");
bytes = test_cmsgsize(so, &src, &dst, CFG_SO_MAX_SEND_BUFFER,
CFG_SO_MAX_SEND_BUFFER/2);
if (bytes < 0)
err(4, "3: got errno");
close(so);
return 0;
}
int
test_cmsgsize(int so, struct in_addr *src, struct in_addr *dst,
unsigned int sndbuf_size, unsigned int payload_size)
{
char cmsgbuf[CMSG_SPACE(sizeof(struct in_addr))];
struct sockaddr_in to;
struct in_addr *source_address;
struct msghdr msg;
struct cmsghdr *cmsg;
struct iovec iov;
if (setsockopt(so, SOL_SOCKET, SO_SNDBUF, &sndbuf_size,
sizeof(sndbuf_size)) < 0)
err(1, "setsockopt send buffer");
/* setup remote address */
memset(&to, 0, sizeof(to));
to.sin_family = AF_INET;
to.sin_addr = *dst;
to.sin_port = htons(CFG_PORT);
/* setup buffer to be sent */
memset(&msg, 0, sizeof(msg));
msg.msg_name = &to;
msg.msg_namelen = sizeof(to);
iov.iov_base = payload;
iov.iov_len = payload_size;
msg.msg_iovlen = 1;
msg.msg_iov = &iov;
/* setup configuration for source address */
memset(cmsgbuf, 0, sizeof(cmsgbuf));
msg.msg_control = cmsgbuf;
msg.msg_controllen = sizeof(cmsgbuf);
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = IPPROTO_IP;
cmsg->cmsg_type = IP_SENDSRCADDR;
cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_addr));
source_address = (struct in_addr *)(CMSG_DATA(cmsg));
memcpy(source_address, src, sizeof(struct in_addr));
return sendmsg(so, &msg, 0);
}
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