dhclient(8): default_route_index(): poll(2) -> ppoll(2)

Use ppoll(2) instead of poll(2) in default_route_index().  Using
ppoll(2) here forces us to use clock_gettime(2) to measure the
timeout, which is less error-prone than using time(3).

Part of a larger campaign in dhclient(8) to make "time stuff" more
accurate and robust.

Prompted by krw@.  Based on a diff from krw@.

ok krw@

diff --git a/sbin/dhclient/kroute.c b/sbin/dhclient/kroute.c
index a92c9b1..b1beeb6 100644 (file)
--- a/sbin/dhclient/kroute.c
+++ b/sbin/dhclient/kroute.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kroute.c,v 1.193 2020/11/25 00:05:48 krw Exp $        */
+/*     $OpenBSD: kroute.c,v 1.194 2021/02/01 16:29:22 cheloha Exp $    */
 
 /*
  * Copyright 2012 Kenneth R Westerback <krw@openbsd.org>
@@ -551,7 +551,7 @@ int
 default_route_index(int rdomain, int routefd)
 {
        struct pollfd            fds[1];
-       time_t                   start_time, cur_time;
+       struct timespec          now, stop, timeout;
        int                      nfds;
        struct iovec             iov[3];
        struct sockaddr_in       sin;
@@ -584,8 +584,10 @@ default_route_index(int rdomain, int routefd)
        iov[2].iov_len = sizeof(sin);
 
        pid = getpid();
-       if (time(&start_time) == -1)
-               fatal("start time");
+       clock_gettime(CLOCK_REALTIME, &now);
+       timespecclear(&timeout);
+       timeout.tv_sec = 3;
+       timespecadd(&now, &timeout, &stop);
 
        if (writev(routefd, iov, 3) == -1) {
                if (errno == ESRCH)
@@ -596,16 +598,19 @@ default_route_index(int rdomain, int routefd)
                return 0;
        }
 
-       do {
-               if (time(&cur_time) == -1)
-                       fatal("current time");
+       for (;;) {
+               clock_gettime(CLOCK_REALTIME, &now);
+               if (timespeccmp(&stop, &now, <=))
+                       break;
+               timespecsub(&stop, &now, &timeout);
+
                fds[0].fd = routefd;
                fds[0].events = POLLIN;
-               nfds = poll(fds, 1, 3);
+               nfds = ppoll(fds, 1, &timeout, NULL);
                if (nfds == -1) {
                        if (errno == EINTR)
                                continue;
-                       log_warn("%s: poll(routefd)", log_procname);
+                       log_warn("%s: ppoll(routefd)", log_procname);
                        break;
                }
                if ((fds[0].revents & (POLLERR | POLLHUP | POLLNVAL)) != 0) {
@@ -636,7 +641,7 @@ default_route_index(int rdomain, int routefd)
                        }
                        return m_rtmsg.m_rtm.rtm_index;
                }
-       } while ((cur_time - start_time) <= 3);
+       }
 
        return 0;
 }