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Subjectdisappearing listen()ed SO_REUSEPORT sockets across fork() when using epoll
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Hello, when running the attached program on 3.12 child processes
are missing a socket fd opened, set with SO_REUSEPORT, listen()ed to,
and added to epoll_ctl().

This is the output I get when pointing "wget http://localhost:5555/"
at the attached program:

main PID 31591
PID 31634 started
PID 31634 accept()ed connection
PID 31635 started
PID 31636 started
PID 31635 accept() failed: Bad file descriptor
PID 31636 accept() failed: Bad file descriptor
PID 31634 accept()ed connection
PID 31634 accept()ed connection
PID 31634 accept()ed connection
PID 31634 accept()ed connection


While I would expect something like:

main PID 31591
PID 31634 started
PID 31634 accept()ed connection
PID 31635 started
PID 31636 started
PID 31635 accept()ed connection
PID 31636 accept()ed connection

-more new processes, but inversely proportional to number of listening processes
-accept() always returns successfully


--

---
Shawn Landden
+1 360 389 3001 (SMS preferred)
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>

int main( int argc, char *argv[]) {
int sockfd, epollfd, acceptfd, portno;
struct epoll_event event = {EPOLLIN, NULL}, gotevent;
char buffer[256];
struct sockaddr_in serv_addr;
int n;
pid_t pid;

printf("main PID %d\n", getpid());

memset((char *) &serv_addr, 0, sizeof(serv_addr));
portno = 5555;
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
return printf("socket() failed: %m\n");

int optval = 1;
if ((setsockopt(sockfd, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval))) < 0)
return printf("setsockopt() failed: %m");

if (bind(sockfd, (struct sockaddr *) &serv_addr,
sizeof(serv_addr)) < 0)
return printf("bind() failed: %m\n");

if (listen(sockfd, SOMAXCONN) < 0)
return printf("listen() failed: %m\n");

if ((epollfd = epoll_create1(0)) < 0)
return printf("epoll_create1() failed: %m\n");

if (epoll_ctl(epollfd, EPOLL_CTL_ADD, sockfd, &event) < 0)
return printf("epoll_ctl() failed: %m\n");

while (1) {
if (epoll_wait(epollfd, &gotevent, 1, -1) != 1)
return printf("epoll_wait() failed: %m\n");

pid = fork();
if (pid == 0) {
printf("PID %d started\n", getpid());
while(1) {
struct sockaddr_in cli_addr;
socklen_t cli_size = sizeof cli_addr;

if ((acceptfd = accept(sockfd, (struct sockaddr *)&cli_addr,
&cli_size)) < 0) {
printf("PID %d accept() failed: %m\n", getpid());
sleep(60);
return 1;
}

printf("PID %d accept()ed connection\n", getpid());

if (close(acceptfd) < 0)
return printf("close() failed: %m\n");
}
}
close(sockfd);
}
}
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