kqueue does not set EV_EOF flag

Andrey N. Oktyabrski ano at bestmx.ru
Tue Sep 6 02:57:18 PDT 2011

Good day.

I have some problems between nginx and backends. Nginx can not see when 
the backend closed connection. The nginx developers said there is a 
kqueue problem. They wrote test program (attached), which works well 
under the FreeBSD and NetBSD, but do not work properly under DragonFly.

Using "select" or "poll" methods in the nginx solves the problem, but 
kqueue is preferred.

$ uname -iprs
DragonFly 2.10-RELEASE x86_64 X86_64_GENERIC_SMP

#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sysexits.h>

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

    int sock[2];
    struct kevent kc;
    int kq;
    char foo[1024];

    if (socketpair(PF_LOCAL, SOCK_STREAM, 0, sock) < 0)
        err(EX_TEMPFAIL, "socketpair");

    if (write(sock[0], foo, sizeof(foo)) < 0)
        err(EX_TEMPFAIL, "write");


    EV_SET(&kc, sock[1], EVFILT_READ, EV_ADD | EV_CLEAR, 0, 0, 0);

    kq = kqueue();
    if (kevent(kq, &kc, 1, NULL, 0, NULL) < 0)
        err(EX_TEMPFAIL, "kqueue");

    if (kevent(kq, NULL, 0, &kc, 1, NULL) < 0)
        err(EX_TEMPFAIL, "kevent1");
    printf("kevent1 done, flags: %04x\n", kc.flags);

    if (kc.flags & EV_EOF) {
        printf("kevent1 reported EOF, exiting\n");

    if (kevent(kq, NULL, 0, &kc, 1, NULL) < 0)
        err(EX_TEMPFAIL, "kevent2");
    printf("kevent2 done, flags: %04x\n", kc.flags);


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