ff_shutdown() not working on UDP sockets

[sarosharif]

I am writing an echo application that calls shutdown to turn off receive side when a certain number of packets are received however ff_shutdown() is not working with UDP sockets.
I tried the same thing with TCP sockets and it is working as expected.

Here is sample code to reproduce the problem:

#include <stdio.h>
#include <sys/ioctl.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <strings.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
#include <assert.h>

#include "ff_config.h"
#include "ff_api.h"
int sockfd;

char clientip[]="14.0.0.17";
int clientport=15310;
int serverport=15310;

int cnt =0;
struct sockaddr_in     servaddr;
int loop(void *arg)
{

    struct sockaddr_in serv_addr;
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(serverport);

    char recv_buf[2048];
    int recv_len;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(serverport);
    inet_pton(AF_INET, "14.0.0.17", &servaddr.sin_addr);
       
    int n, len;

    recv_len = ff_recvfrom(sockfd, (char *)recv_buf, 2048, MSG_WAITALL, (struct sockaddr *) &servaddr,&len);
    if (recv_len>0)
    {
        printf("recv_len = %d\n", recv_len);
        printf("Recv: %s \n", recv_buf);
        cnt ++;
    }
    if (cnt == 3)
    {
        printf("shutting down recv side\n");
        cnt++;
        ff_shutdown(sockfd,0);
    }
    
    struct sockaddr_in remote_addr;
    memset(&remote_addr, 0, sizeof(remote_addr));
    remote_addr.sin_family = AF_INET;
    remote_addr.sin_port = htons(clientport);
    remote_addr.sin_addr.s_addr = inet_addr(clientip);

    ff_sendto(sockfd, recv_buf, strlen(recv_buf) + 1, 0, (struct linux_sockaddr *)&remote_addr, sizeof(remote_addr));

}



int main(int argc, char *argv[])
{

    ff_init(argc, argv);
    sockfd = ff_socket(AF_INET, SOCK_DGRAM, 0);
    
    if (sockfd < 0)
    {
        printf("ff_socket failed\n");
        exit(1);
    }

    ff_run(loop, NULL);
    return 0;
}

[jfb8856606]

In FreeBSD, udp_shutdown() calls sorflush() which sets SS_CANTRCVMORE on the socket and should wake up threads blocked in recv(). The ENOTCONN return value for unconnected UDP sockets is POSIX-compliant behavior.

F-Stack ports the FreeBSD user-space stack, and the wakeup() mechanism for unblocking sbwait() may behave differently in user-space. We will investigate this further. If you can provide a minimal reproduction case (exact sequence of ff_socket → ff_bind → ff_recv (blocked) → ff_shutdown from another thread), it would help with debugging.