userland - dhclient - Fix possible infinite loop from unhandled poll(2) return

[dragonfly.git] / sbin / dhclient / dhclient.c

diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c
index 1d78829..9d421ed 100644 (file)
--- a/sbin/dhclient/dhclient.c
+++ b/sbin/dhclient/dhclient.c
@@ -57,6 +57,7 @@
 #include <ctype.h>
 #include <poll.h>
 #include <pwd.h>
+#include <unistd.h>
 
 #include "dhcpd.h"
 #include "privsep.h"
@@ -64,6 +65,8 @@
 #define        CLIENT_PATH             "PATH=/usr/bin:/usr/sbin:/bin:/sbin"
 #define DEFAULT_LEASE_TIME     43200   /* 12 hours... */
 #define TIME_MAX               2147483647
+#define POLL_FAILURES          10
+#define POLL_FAILURE_WAIT      1       /* Back off multiplier (seconds) */
 
 time_t cur_time;
 
@@ -2123,7 +2126,7 @@ int
 fork_privchld(int fd, int fd2)
 {
        struct pollfd pfd[1];
-       int nfds;
+       int nfds, pfail = 0;
 
        switch (fork()) {
        case -1:
@@ -2153,8 +2156,16 @@ fork_privchld(int fd, int fd2)
                        if (errno != EINTR)
                                error("poll error");
 
-               if (nfds == 0 || !(pfd[0].revents & POLLIN))
+               /*
+                * Handle temporary errors, but bail if they persist.
+                */
+               if (nfds == 0 || !(pfd[0].revents & POLLIN)) {
+                       if (pfail > POLL_FAILURES)
+                               error("poll failed > %d times", POLL_FAILURES);
+                       sleep(pfail * POLL_FAILURE_WAIT);
+                       pfail++;
                        continue;
+               }
 
                dispatch_imsg(fd);
        }