HedongGao opened a new pull request, #17699:
URL: https://github.com/apache/nuttx/pull/17699
## Summary
According to RFC768 page2 and referring to the Linux implementation, the
message with udp length of 0 is supported.
## Impact
Users are allowed to send udp messages with length 0.
## Testing
Change the code of nutt-apps/examples/udp/udpclient.c as follow:
`
void udp_client(void)
{
#ifdef CONFIG_EXAMPLES_UDP_IPv6
struct sockaddr_in6 server;
#else
struct sockaddr_in server;
#endif
unsigned char outbuf[SENDSIZE];
socklen_t addrlen;
int sockfd;
int nbytes;
int offset;
#ifdef CONFIG_EXAMPLES_UDP_BROADCAST
int optval;
int ret;
#endif
/* Create a new UDP socket */
sockfd = create_socket();
if (sockfd < 0)
{
printf("client ERROR: create_socket failed\n");
exit(1);
}
#ifdef CONFIG_EXAMPLES_UDP_BROADCAST
optval = 1;
ret = setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(int));
if (ret < 0)
{
printf("Failed to set SO_BROADCAST\n");
exit(1);
}
#endif
/* Set up the server address */
#ifdef CONFIG_EXAMPLES_UDP_IPv6
server.sin6_family = AF_INET6;
server.sin6_port = HTONS(CONFIG_EXAMPLES_UDP_SERVER_PORTNO);
memcpy(server.sin6_addr.s6_addr16,
g_udpserver_ipv6, 8 * sizeof(uint16_t));
addrlen = sizeof(struct sockaddr_in6);
#else
server.sin_family = AF_INET;
server.sin_port = HTONS(CONFIG_EXAMPLES_UDP_SERVER_PORTNO);
server.sin_addr.s_addr = (in_addr_t)g_udpserver_ipv4;
addrlen = sizeof(struct sockaddr_in);
#endif
/* Then send and receive 256 messages */
for (offset = 0; offset < 20; offset++)
{
/* Set up the output buffer */
fill_buffer(outbuf, offset);
/* Send the message */
printf("client: %d. Sending %d bytes\n", offset, SENDSIZE);
nbytes = sendto(sockfd, outbuf, SENDSIZE, 0,
(struct sockaddr *)&server, addrlen);
printf("client: %d. Sent %d bytes\n", offset, nbytes);
if (nbytes < 0)
{
printf("client: %d. sendto failed: %d\n", offset, errno);
close(sockfd);
exit(-1);
}
else if (nbytes != SENDSIZE)
{
printf("client: %d. Bad send length: %d Expected: %d\n",
offset, nbytes, SENDSIZE);
close(sockfd);
exit(-1);
}
/* Now, sleep a bit. No packets should be dropped due to overrunning
* the server.
*/
sleep(1);
}
for (offset = 0; offset < 20; offset++)
{
/* Send the message */
printf("client: %d. Sending %d bytes\n", offset, 0);
nbytes = sendto(sockfd, outbuf, 0, 0,
(struct sockaddr *)&server, addrlen);
printf("client: %d. Sent %d bytes\n", offset, 0);
if (nbytes < 0)
{
printf("client: %d. sendto failed: %d\n", offset, errno);
close(sockfd);
exit(-1);
}
else if (nbytes != 0)
{
printf("client: %d. Bad send length: %d Expected: %d\n",
offset, nbytes, 0);
close(sockfd);
exit(-1);
}
/* Now, sleep a bit. No packets should be dropped due to overrunning
* the server.
*/
sleep(1);
}
close(sockfd);
}
`
Open the compilation configuration of CONFIG_EXAMPLES_UDP, compile
udpclient, build the SIM environment, and allow udpclient in sim and udpserver
on the host side. The server can receive UDP messages with length 0.
`
16:00:21.820640 IP (tos 0x0, ttl 64, id 110, offset 0, flags [DF], proto UDP
(17), length 124)
10.0.1.2.5472 > 10.0.0.1.5471: [udp sum ok] UDP, length 96
16:00:22.830757 IP (tos 0x0, ttl 64, id 111, offset 0, flags [DF], proto UDP
(17), length 28)
10.0.1.2.5472 > 10.0.0.1.5471: [udp sum ok] UDP, length 0
16:00:23.840546 IP (tos 0x0, ttl 64, id 112, offset 0, flags [DF], proto UDP
(17), length 28)
10.0.1.2.5472 > 10.0.0.1.5471: [udp sum ok] UDP, length 0
`
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