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// SPDX-License-Identifier: GPL-2.0-or-later
/* recv-zero.c
*
* Verify that we're able to discard datagrams by recv()ing into a zero-length
* buffer.
*
* Copyright Red Hat
* Author: David Gibson <david@gibson.dropbear.id.au>
*/
#include <arpa/inet.h>
#include <errno.h>
#include <net/if.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "common.h"
#define DSTPORT 13257U
enum discard_method {
DISCARD_NULL_BUF,
DISCARD_ZERO_IOV,
DISCARD_NULL_IOV,
NUM_METHODS,
};
/* 127.0.0.1:DSTPORT */
static const struct sockaddr_in lo_dst = SOCKADDR_INIT(INADDR_LOOPBACK, DSTPORT);
static void test_discard(enum discard_method method)
{
struct iovec zero_iov = { .iov_base = NULL, .iov_len = 0, };
struct msghdr mh_zero = {
.msg_iov = &zero_iov,
.msg_iovlen = 1,
};
struct msghdr mh_null = {
.msg_iov = NULL,
.msg_iovlen = 0,
};
long token1, token2;
int recv_s, send_s;
ssize_t rc;
token1 = random();
token2 = random();
recv_s = sock_reuseaddr();
if (bind(recv_s, (struct sockaddr *)&lo_dst, sizeof(lo_dst)) < 0)
die("bind(): %s\n", strerror(errno));
send_s = sock_reuseaddr();
if (connect(send_s, (struct sockaddr *)&lo_dst, sizeof(lo_dst)) < 0)
die("connect(): %s\n", strerror(errno));
send_token(send_s, token1);
send_token(send_s, token2);
switch (method) {
case DISCARD_NULL_BUF:
/* cppcheck-suppress nullPointer */
rc = recv(recv_s, NULL, 0, MSG_DONTWAIT);
if (rc < 0)
die("discarding recv(): %s\n", strerror(errno));
break;
case DISCARD_ZERO_IOV:
rc = recvmsg(recv_s, &mh_zero, MSG_DONTWAIT);
if (rc < 0)
die("recvmsg() with zero-length buffer: %s\n",
strerror(errno));
if (!((unsigned)mh_zero.msg_flags & MSG_TRUNC))
die("Missing MSG_TRUNC flag\n");
break;
case DISCARD_NULL_IOV:
rc = recvmsg(recv_s, &mh_null, MSG_DONTWAIT);
if (rc < 0)
die("recvmsg() with zero-length iov: %s\n",
strerror(errno));
if (!((unsigned)mh_null.msg_flags & MSG_TRUNC))
die("Missing MSG_TRUNC flag\n");
break;
default:
die("Bad method\n");
}
recv_token(recv_s, token2);
/* cppcheck-suppress nullPointer */
rc = recv(recv_s, NULL, 0, MSG_DONTWAIT);
if (rc < 0 && errno != EAGAIN)
die("redundant discarding recv(): %s\n", strerror(errno));
if (rc >= 0)
die("Unexpected receive: rc=%zd\n", rc);
}
int main(int argc, char *argv[])
{
enum discard_method method;
(void)argc;
(void)argv;
for (method = 0; method < NUM_METHODS; method++)
test_discard(method);
printf("Discarding datagrams with 0-length receives seems to work\n");
exit(0);
}
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