[src/trunk]: src/sys/netinet Move the offset addition in one place and mask t...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0cd91ac4d8bd
branches:  trunk
changeset: 960147:0cd91ac4d8bd
user:      christos <christos%NetBSD.org@localhost>
date:      Tue Mar 09 13:48:16 2021 +0000

description:
Move the offset addition in one place and mask the random generated value
to make sure that the isn is monotonic.

diffstat:

 sys/netinet/tcp_subr.c |  20 ++++++++++----------
 1 files changed, 10 insertions(+), 10 deletions(-)

diffs (50 lines):

diff -r 8a2c71435549 -r 0cd91ac4d8bd sys/netinet/tcp_subr.c
--- a/sys/netinet/tcp_subr.c    Tue Mar 09 12:42:46 2021 +0000
+++ b/sys/netinet/tcp_subr.c    Tue Mar 09 13:48:16 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tcp_subr.c,v 1.287 2021/03/08 18:17:27 christos Exp $  */
+/*     $NetBSD: tcp_subr.c,v 1.288 2021/03/09 13:48:16 christos Exp $  */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -91,7 +91,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tcp_subr.c,v 1.287 2021/03/08 18:17:27 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tcp_subr.c,v 1.288 2021/03/09 13:48:16 christos Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -2210,23 +2210,23 @@
 #ifdef TCPISS_DEBUG
                printf("ISS hash 0x%08x, ", tcp_iss);
 #endif
-               /*
-                * Add the offset in to the computed value.
-                */
-               tcp_iss += tcp_iss_seq;
-#ifdef TCPISS_DEBUG
-               printf("ISS %08x\n", tcp_iss);
-#endif
        } else {
                /*
                 * Randomize.
                 */
-               tcp_iss = cprng_fast32();
+               tcp_iss = cprng_fast32() & TCP_ISS_RANDOM_MASK;
 #ifdef TCPISS_DEBUG
                printf("ISS random 0x%08x, ", tcp_iss);
 #endif
        }
 
+       /*
+        * Add the offset in to the computed value.
+        */
+       tcp_iss += tcp_iss_seq;
+#ifdef TCPISS_DEBUG
+       printf("ISS %08x\n", tcp_iss);
+#endif
        return tcp_iss;
 }