Unix: Rework of select-loop to poll-loop

This should lift the limit of FD_SETSIZE and allow more than 1024 fd's.
FD_SETSIZE limit doesn't matter now when creating new sockets.

sysdep/unix/io.c

@@ -19,6 +19,7 @@
 #include <sys/socket.h>
 #include <sys/uio.h>
 #include <sys/un.h>
+#include <poll.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
@@ -41,12 +42,12 @@
 #include "lib/sysio.h"
 
 /* Maximum number of calls of tx handler for one socket in one
- * select iteration. Should be small enough to not monopolize CPU by
+ * poll iteration. Should be small enough to not monopolize CPU by
  * one protocol instance.
  */
 #define MAX_STEPS 4
 
-/* Maximum number of calls of rx handler for all sockets in one select
+/* Maximum number of calls of rx handler for all sockets in one poll
    iteration. RX callbacks are often much more costly so we limit
    this to gen small latencies */
 #define MAX_RX_STEPS 4
@@ -1022,7 +1023,6 @@ sk_log_error(sock *s, const char *p)
 static list sock_list;
 static struct birdsock *current_sock;
 static struct birdsock *stored_sock;
-static int sock_recalc_fdsets_p;
 
 static inline sock *
 sk_next(sock *s)
@@ -1078,7 +1078,6 @@ sk_free(resource *r)
     if (s == stored_sock)
       stored_sock = sk_next(s);
     rem_node(&s->n);
-    sock_recalc_fdsets_p = 1;
   }
 }
 
@@ -1276,7 +1275,6 @@ static void
 sk_insert(sock *s)
 {
   add_tail(&sock_list, &s->n);
-  sock_recalc_fdsets_p = 1;
 }
 
 static void
@@ -1328,18 +1326,6 @@ sk_passive_connected(sock *s, int type)
       log(L_WARN "SOCK: Cannot get remote IP address for TCP<");
   }
 
-  if (fd >= FD_SETSIZE)
-  {
-    /* FIXME: Call err_hook instead ? */
-    log(L_ERR "SOCK: Incoming connection from %I%J (port %d) %s",
-	t->daddr, ipa_is_link_local(t->daddr) ? t->iface : NULL,
-	t->dport, "rejected due to FD_SETSIZE limit");
-    close(fd);
-    t->fd = -1;
-    rfree(t);
-    return 1;
-  }
-
   if (sk_setup(t) < 0)
   {
     /* FIXME: Call err_hook instead ? */
@@ -1416,9 +1402,6 @@ sk_open(sock *s)
   if (fd < 0)
     ERR("socket");
 
-  if (fd >= FD_SETSIZE)
-    ERR2("FD_SETSIZE limit reached");
-
   s->af = af;
   s->fd = fd;
 
@@ -2062,15 +2045,15 @@ static int short_loops = 0;
 void
 io_loop(void)
 {
-  fd_set rd, wr;
+  int poll_tout;
-  struct timeval timo;
   time_t tout;
-  int hi, events;
+  int nfds, events;
   sock *s;
   node *n;
+  int fdmax = 256;
+  struct pollfd *pfd = xmalloc(fdmax * sizeof(struct pollfd));
 
   watchdog_start1();
-  sock_recalc_fdsets_p = 1;
   for(;;)
     {
       events = ev_run_list(&global_event_list);
@@ -2081,43 +2064,43 @@ io_loop(void)
 	  tm_shot();
 	  continue;
 	}
-      timo.tv_sec = events ? 0 : MIN(tout - now, 3);
+      poll_tout = (events ? 0 : MIN(tout - now, 3)) * 1000; /* Time in milliseconds */
-      timo.tv_usec = 0;
 
       io_close_event();
 
-      if (sock_recalc_fdsets_p)
+      nfds = 0;
-	{
-	  sock_recalc_fdsets_p = 0;
-	  FD_ZERO(&rd);
-	  FD_ZERO(&wr);
-	}
-
-      hi = 0;
       WALK_LIST(n, sock_list)
 	{
+	  pfd[nfds] = (struct pollfd) { .fd = -1 }; /* everything other set to 0 by this */
 	  s = SKIP_BACK(sock, n, n);
 	  if (s->rx_hook)
 	    {
-	      FD_SET(s->fd, &rd);
+	      pfd[nfds].fd = s->fd;
-	      if (s->fd > hi)
+	      pfd[nfds].events |= POLLIN;
-		hi = s->fd;
 	    }
-	  else
-	    FD_CLR(s->fd, &rd);
 	  if (s->tx_hook && s->ttx != s->tpos)
 	    {
-	      FD_SET(s->fd, &wr);
+	      pfd[nfds].fd = s->fd;
-	      if (s->fd > hi)
+	      pfd[nfds].events |= POLLOUT;
-		hi = s->fd;
+	    }
+	  if (pfd[nfds].fd != -1)
+	    {
+	      s->index = nfds;
+	      nfds++;
 	    }
 	  else
-	    FD_CLR(s->fd, &wr);
+	    s->index = -1;
+
+	  if (nfds >= fdmax)
+	    {
+	      fdmax *= 2;
+	      pfd = xrealloc(pfd, fdmax * sizeof(struct pollfd));
+	    }
 	}
 
       /*
        * Yes, this is racy. But even if the signal comes before this test
-       * and entering select(), it gets caught on the next timer tick.
+       * and entering poll(), it gets caught on the next timer tick.
        */
 
       if (async_config_flag)
@@ -2142,18 +2125,18 @@ io_loop(void)
 	  continue;
 	}
 
-      /* And finally enter select() to find active sockets */
+      /* And finally enter poll() to find active sockets */
       watchdog_stop();
-      hi = select(hi+1, &rd, &wr, NULL, &timo);
+      events = poll(pfd, nfds, poll_tout);
       watchdog_start();
 
-      if (hi < 0)
+      if (events < 0)
 	{
 	  if (errno == EINTR || errno == EAGAIN)
 	    continue;
-	  die("select: %m");
+	  die("poll: %m");
 	}
-      if (hi)
+      if (events)
 	{
 	  /* guaranteed to be non-empty */
 	  current_sock = SKIP_BACK(sock, n, HEAD(sock_list));
@@ -2161,11 +2144,17 @@ io_loop(void)
 	  while (current_sock)
 	    {
 	      sock *s = current_sock;
+	      if (s->index == -1)
+		{
+		  current_sock = sk_next(s);
+		  goto next;
+		}
+
 	      int e;
 	      int steps;
 
 	      steps = MAX_STEPS;
-	      if ((s->type >= SK_MAGIC) && FD_ISSET(s->fd, &rd) && s->rx_hook)
+	      if ((s->type >= SK_MAGIC) && (pfd[s->index].revents & (POLLIN | POLLHUP | POLLERR)) && s->rx_hook)
 		do
 		  {
 		    steps--;
@@ -2177,7 +2166,7 @@ io_loop(void)
 		while (e && s->rx_hook && steps);
 
 	      steps = MAX_STEPS;
-	      if (FD_ISSET(s->fd, &wr))
+	      if (pfd[s->index].revents & POLLOUT)
 		do
 		  {
 		    steps--;
@@ -2204,13 +2193,17 @@ io_loop(void)
 	  while (current_sock && count < MAX_RX_STEPS)
 	    {
 	      sock *s = current_sock;
-	      int e UNUSED;
+	      if (s->index == -1)
+		{
+		  current_sock = sk_next(s);
+		  goto next2;
+		}
 
-	      if ((s->type < SK_MAGIC) && FD_ISSET(s->fd, &rd) && s->rx_hook)
+	      if ((s->type < SK_MAGIC) && (pfd[s->index].revents & (POLLIN | POLLHUP | POLLERR)) && s->rx_hook)
 		{
 		  count++;
 		  io_log_event(s->rx_hook, s->data);
-		  e = sk_read(s);
+		  sk_read(s);
 		  if (s != current_sock)
 		      goto next2;
 		}