sock.c

   1 // Copyright 2011 Keith Rarick. See file COPYING for details.
   2
   3 #include <stdlib.h>
   4 #include <sys/resource.h>
   5 #include <event.h>
   6 #include "dat.h"
   7
   8 static void handleev(const int fd, const short ev, Socket *s);
   9 static void nudge_fd_limit();
  10 static Handle tick;
  11 static void   *tickval;
  12
  13 static struct timeval ival;
  14
  15
  16 void
  17 sockinit(Handle f, void *x, int64 i)
  18 {
  19     tick = f;
  20     tickval = x;
  21     init_timeval(&ival, i);
  22     event_init();
  23     nudge_fd_limit();
  24 }
  25
  26
  27 int
  28 sockwant(Socket *s, int rw)
  29 {
  30     int r;
  31
  32     if (s->added) {
  33         r = event_del(&s->evq);
  34         if (r == -1) {
  35             return -1;
  36         }
  37     }
  38     s->added = 1;
  39     if (rw) {
  40         int mask = 0;
  41
  42         switch (rw) {
  43         case 't':
  44             // fake a global timeout with libevent
  45             event_set(&s->evq, s->fd, EV_READ|EV_PERSIST, (evh)handleev, s);
  46             return event_add(&s->evq, &ival);
  47         case 'r':
  48             mask = EV_READ;
  49             break;
  50         case 'w':
  51             mask = EV_WRITE;
  52             break;
  53         }
  54         event_set(&s->evq, s->fd, mask|EV_PERSIST, (evh)handleev, s);
  55         return event_add(&s->evq, 0);
  56     }
  57     return 0;
  58 }
  59
  60
  61 void
  62 sockmain()
  63 {
  64     event_dispatch();
  65 }
  66
  67
  68 static void
  69 handleev(const int fd, const short ev, Socket *s)
  70 {
  71     switch (ev) {
  72     case EV_TIMEOUT:
  73         // libevent removes the fd if it timed out, so put it back
  74         event_add(&s->evq, &ival);
  75         tick(tickval, 0);
  76         break;
  77     case EV_READ:
  78         s->f(s->x, 'r');
  79         break;
  80     case EV_WRITE:
  81         s->f(s->x, 'w');
  82         break;
  83     }
  84 }
  85
  86
  87 /* This is a workaround for a mystifying workaround in libevent's epoll
  88  * implementation. The epoll_init() function creates an epoll fd with space to
  89  * handle RLIMIT_NOFILE - 1 fds, accompanied by the following puzzling comment:
  90  * "Solaris is somewhat retarded - it's important to drop backwards
  91  * compatibility when making changes. So, don't dare to put rl.rlim_cur here."
  92  * This is presumably to work around a bug in Solaris, but it has the
  93  * unfortunate side-effect of causing epoll_ctl() (and, therefore, event_add())
  94  * to fail for a valid fd if we have hit the limit of open fds. That makes it
  95  * hard to provide reasonable behavior in that situation. So, let's reduce the
  96  * real value of RLIMIT_NOFILE by one, after epoll_init() has run. */
  97 static void
  98 nudge_fd_limit()
  99 {
 100     int r;
 101     struct rlimit rl;
 102
 103     r = getrlimit(RLIMIT_NOFILE, &rl);
 104     if (r != 0) twarn("getrlimit(RLIMIT_NOFILE)"), exit(2);
 105
 106     rl.rlim_cur--;
 107
 108     r = setrlimit(RLIMIT_NOFILE, &rl);
 109     if (r != 0) twarn("setrlimit(RLIMIT_NOFILE)"), exit(2);
 110 }