--- tcp_scan.c.orig     Tue Apr  4 09:33:08 1995
+++ tcp_scan.c  Mon Jun  5 09:05:14 1995
@@ -3,6 +3,7 @@
   * and detect telnet options
   * 
   * Author: Wietse Venema.
+  * Linux modifications to use exceptfds in select() call: Larry Doolittle
   */
 
 #include <sys/types.h>
@@ -62,6 +63,7 @@
 struct timeval now;                    /* banner_info last update time */
 fd_set  write_socket_mask;             /* sockets with connect() in progress */
 fd_set  read_socket_mask;              /* sockets with connect() finished */
+fd_set  except_socket_mask;            /* sockets with either of above */
 int     ports_busy;                    /* number of open sockets */
 int     ports_done;                    /* number of finished sockets */
 int     max_sock;                      /* max socket file descriptor */
@@ -159,6 +161,7 @@
 
     FD_ZERO(&write_socket_mask);
     FD_ZERO(&read_socket_mask);
+    FD_ZERO(&except_socket_mask);
     ports_busy = 0;
 
     /*
@@ -256,8 +259,9 @@
 {
     fd_set  read_mask;
     fd_set  write_mask;
-    static struct timeval waitsome = {1, 1,};
-    static struct timeval waitnot = {0, 0,};
+    fd_set  except_mask;
+    struct timeval waitsome = {1, 1,};
+    struct timeval waitnot = {0, 0,};
     int     sock;
     char    ch;
 
@@ -266,15 +270,16 @@
        /*
         * When a connect() completes, report the socket and get rid of it.
         */
-       write_mask = write_socket_mask;
-       read_mask = read_socket_mask;
-       if (select(max_sock + 1, &read_mask, &write_mask, (fd_set *) 0,
+       write_mask  = write_socket_mask;
+       read_mask   = read_socket_mask;
+       except_mask = except_socket_mask;
+       if (select(max_sock + 1, &read_mask, &write_mask, &except_mask,
                   wait ? (struct timeval *) 0 : &waitnot) < 0)
            error("select: %m");
        if (FD_ISSET(icmp_sock, &read_mask))
            receive_icmp(icmp_sock);
        for (sock = 0; ports_busy > 0 && sock <= max_sock; sock++) {
-           if (FD_ISSET(sock, &write_mask)) {
+           if (FD_ISSET(sock, &write_mask) || FD_ISSET(sock,&except_mask)) {
                if (read(sock, &ch, 1) < 0 && errno != EWOULDBLOCK && errno != EAGAIN) {
                    report_and_drop_socket(sock, errno);
                } else {
@@ -289,9 +294,10 @@
         * banner_time seconds. Assume we have received all banner data when
         * a socket stops sending for BANNER_IDLE seconds.
         */
-       write_mask = write_socket_mask;
-       read_mask = read_socket_mask;
-       if (select(max_sock + 1, &read_mask, &write_mask, (fd_set *) 0,
+       write_mask  = write_socket_mask;
+       read_mask   = read_socket_mask;
+       except_mask = except_socket_mask;
+       if (select(max_sock + 1, &read_mask, &write_mask, &except_mask,
                   wait ? &waitsome : &waitnot) < 0)
            error("select: %m");
        if (FD_ISSET(icmp_sock, &read_mask))
@@ -316,6 +322,12 @@
                    report_and_drop_socket(sock, 0);
                    break;
                }
+           } else if (FD_ISSET(sock, &except_mask)) {
+               if (read(sock, &ch, 1) < 0 && errno != EWOULDBLOCK && errno != EAGAIN) {
+                   report_and_drop_socket(sock, errno);
+               } else {
+                   report_and_drop_socket(sock, 0);
+               }
            } else if (FD_ISSET(sock, &read_socket_mask)) {
                if (time_since_connect(sock) > banner_time
                    || time_since_read(sock) > BANNER_IDLE)
@@ -417,6 +429,7 @@
        bp->flags = 0;
     }
     FD_SET(sock, &write_socket_mask);
+    FD_SET(sock, &except_socket_mask);
     if (sock > max_sock)
        max_sock = sock;
     ports_busy++;
@@ -434,6 +447,7 @@
     close(sock);
     FD_CLR(sock, &read_socket_mask);
     FD_CLR(sock, &write_socket_mask);
+    FD_CLR(sock, &except_socket_mask);
     ports_busy--;
     ports_done++;
 }