Ephemeral port selection (patch)

[Fernando Gont]

Folks,

This patch simply eliminates duplicated code in the in_pcb_bind() function.

Index: in_pcb.c
===================================================================
RCS file: /home/ncvs/src/sys/netinet/in_pcb.c,v
retrieving revision 1.198
diff -u -r1.198 in_pcb.c
--- in_pcb.c    22 Dec 2007 10:06:11 -0000      1.198
+++ in_pcb.c    25 Feb 2008 06:10:04 -0000
@@ -393,7 +393,7 @@
         if (*lportp != 0)
                 lport = *lportp;
         if (lport == 0) {
-               u_short first, last;
+               u_short first, last, aux;
                 int count;

                 if (laddr.s_addr != INADDR_ANY)
@@ -440,47 +440,28 @@
                 /*
                  * Simple check to ensure all ports are not used up causing
                  * a deadlock here.
-                *
-                * We split the two cases (up and down) so that the direction
-                * is not being tested on each round of the loop.
                  */
                 if (first > last) {
-                       /*
-                        * counting down
-                        */
-                       if (dorandom)
-                               *lastport = first -
-                                           (arc4random() % (first - last));
-                       count = first - last;
-
-                       do {
-                               if (count-- < 0)        /* completely used? */
-                                       return (EADDRNOTAVAIL);
-                               --*lastport;
-                               if (*lastport > first || *lastport < last)
-                                       *lastport = first;
-                               lport = htons(*lastport);
-                       } while (in_pcblookup_local(pcbinfo, laddr, lport,
-                           wild));
-               } else {
-                       /*
-                        * counting up
-                        */
-                       if (dorandom)
-                               *lastport = first +
-                                           (arc4random() % (last - first));
-                       count = last - first;
-
-                       do {
-                               if (count-- < 0)        /* completely used? */
-                                       return (EADDRNOTAVAIL);
-                               ++*lastport;
-                               if (*lastport < first || *lastport > last)
-                                       *lastport = first;
-                               lport = htons(*lastport);
-                       } while (in_pcblookup_local(pcbinfo, laddr, lport,
-                           wild));
+                       aux = first;
+                       first = last;
+                       last = aux;
                 }
+
+               if (dorandom)
+                       *lastport = first +
+                                   (arc4random() % (last - first));
+
+               count = last - first;
+
+               do {
+                       if (count-- < 0)        /* completely used? */
+                               return (EADDRNOTAVAIL);
+                       ++*lastport;
+                       if (*lastport < first || *lastport > last)
+                               *lastport = first;
+                       lport = htons(*lastport);
+               } while (in_pcblookup_local(pcbinfo, laddr, lport,
+                   wild));
         }
         if (prison_ip(cred, 0, &laddr.s_addr))
                 return (EINVAL);


--
Fernando Gont
e-mail: fernando at gont.com.ar || fgont at acm.org
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1