Avoid alarm to prevent the setitimer interval from being reset

diff --git a/lib/ip/res_send.c b/lib/ip/res_send.c
index 1c6dbe4c1f2eefbc86bd79750dc8bea9a57798a4..88090f3f1a1bd4f74e16734b1cfcb9f4915d0d87 100755 (executable)
--- a/lib/ip/res_send.c
+++ b/lib/ip/res_send.c
@@ -56,6 +56,7 @@ static char sccsid[] = "@(#)res_send.c        6.27 (Berkeley) 2/24/91";
 
 #include <sys/types.h>
 #include <sys/ioctl.h>
+#include <sys/select.h>
 #include <sys/stat.h>
 #include <assert.h>
 #include <errno.h>
@@ -87,7 +88,6 @@ static int udp_sendto _ARGS(( int fd, const char *buf, unsigned buflen,
                                ipaddr_t addr, Udpport_t port ));
 static int udp_receive _ARGS(( int fd, char *buf, unsigned buflen,
                                time_t timeout ));
-static void alarm_handler _ARGS(( int sig ));
 
 #endif /* !_MINIX */
 
@@ -843,13 +843,6 @@ udpport_t port;
        return r;
 }
 
-static void alarm_handler(sig)
-int sig;
-{
-       signal(SIGALRM, alarm_handler);
-       alarm(1);
-}
-
 static int udp_receive(fd, buf, buflen, timeout)
 int fd;
 char *buf;
@@ -859,45 +852,49 @@ time_t timeout;
        char *newbuf;
        udp_io_hdr_t *udp_io_hdr;
        int r, terrno;
-       void (*u_handler) _ARGS(( int sig ));
-       time_t u_timeout;
-
-       newbuf= malloc(sizeof(*udp_io_hdr) + buflen);
+       fd_set readfds;
+       struct timeval timeval;
+       
+       /* allocate buffer for packet */
+       newbuf = malloc(sizeof(*udp_io_hdr) + buflen);
        if (newbuf == NULL)
        {
-               errno= ENOMEM;
+               errno = ENOMEM;
                return -1;
        }
+       
+       /* only read if there is something to be read within timeout seconds */
+       FD_ZERO(&readfds);
+       FD_SET(fd, &readfds);
+       timeval.tv_sec = timeout;
+       timeval.tv_usec = 0;
+       r = select(fd + 1, &readfds, NULL, NULL, &timeval);
+       if (r >= 0 && !FD_ISSET(fd, &readfds))
+       {
+               errno = EINTR;
+               r = -1;
+       }
 
-       u_handler= signal(SIGALRM, alarm_handler);
-       u_timeout= alarm(timeout);
-
-       r= read(fd, newbuf, sizeof(*udp_io_hdr) + buflen);
-       terrno= errno;
+       if (r >= 0)
+               r = read(fd, newbuf, sizeof(*udp_io_hdr) + buflen);
 
+       /* clean up in case of failure */
+       terrno = errno;
        if (r < 0 || r <= sizeof(*udp_io_hdr))
        {
                if (r > 0)
-                       r= 0;
-               free(newbuf);
-
-
-               alarm(0);
-               signal(SIGALRM, u_handler);
-               alarm(u_timeout);
+                       r = 0;
 
-               errno= terrno;
+               free(newbuf);
+               errno = terrno;
                return r;
        }
 
+       /* copy packet body to caller-provided buffer */
        memcpy(buf, newbuf + sizeof(*udp_io_hdr), r - sizeof(*udp_io_hdr));
        free(newbuf);
 
-       alarm(0);
-       signal(SIGALRM, u_handler);
-       alarm(u_timeout);
-
-       return r-sizeof(*udp_io_hdr);
+       return r - sizeof(*udp_io_hdr);
 }
 
 #endif