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