From a48370d5e99d81328d5890253eca42817fd33aae Mon Sep 17 00:00:00 2001
From: jifl <jifl>
Date: Mon, 10 Mar 2008 16:12:31 +0000
Subject: [PATCH]   * inet_chksum.c: Allow choice of one of the sample
 algorithms to be     made from lwipopts.h. Fix comment on how to override
 LWIP_CHKSUM.

---
 CHANGELOG                   |  4 ++++
 src/core/ipv4/inet_chksum.c | 28 +++++++++++++++++++---------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 1781b64a..f2e46370 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -19,6 +19,10 @@ HISTORY
 
   ++ New features:
 
+  2008-03-10 Jonathan Larmour
+  * inet_chksum.c: Allow choice of one of the sample algorithms to be
+    made from lwipopts.h. Fix comment on how to override LWIP_CHKSUM.
+
   2008-01-22 Frédéric Bernon
   * tcp.c, tcp_in.c, tcp.h, opt.h: Rename LWIP_CALCULATE_EFF_SEND_MSS in 
     TCP_CALCULATE_EFF_SEND_MSS to have coherent TCP options names.
diff --git a/src/core/ipv4/inet_chksum.c b/src/core/ipv4/inet_chksum.c
index 9bba4f4c..bc492fea 100644
--- a/src/core/ipv4/inet_chksum.c
+++ b/src/core/ipv4/inet_chksum.c
@@ -46,14 +46,26 @@
 /* These are some reference implementations of the checksum algorithm, with the
  * aim of being simple, correct and fully portable. Checksumming is the
  * first thing you would want to optimize for your platform. If you create
- * your own version, link it in and in your sys_arch.h put:
+ * your own version, link it in and in your cc.h put:
  * 
  * #define LWIP_CHKSUM <your_checksum_routine> 
-*/
-#ifndef LWIP_CHKSUM
-#define LWIP_CHKSUM lwip_standard_chksum
+ *
+ * Or you can select from the implementations below by defining
+ * LWIP_CHKSUM_ALGORITHM to 1, 2 or 3.
+ */
 
-#if 1 /* Version A */
+#ifndef LWIP_CHKSUM
+# define LWIP_CHKSUM lwip_standard_chksum
+# ifndef LWIP_CHKSUM_ALGORITHM
+#  define LWIP_CHKSUM_ALGORITHM 1
+# endif
+#endif
+/* If none set: */
+#ifndef LWIP_CHKSUM_ALGORITHM
+# define LWIP_CHKSUM_ALGORITHM 0
+#endif
+
+#if (LWIP_CHKSUM_ALGORITHM == 1) /* Version #1 */
 /**
  * lwip checksum
  *
@@ -104,7 +116,7 @@ lwip_standard_chksum(void *dataptr, u16_t len)
 }
 #endif
 
-#if 0 /* Version B */
+#if (LWIP_CHKSUM_ALGORITHM == 2) /* Alternative version #2 */
 /*
  * Curt McDowell
  * Broadcom Corp.
@@ -160,7 +172,7 @@ lwip_standard_chksum(void *dataptr, int len)
 }
 #endif
 
-#if 0 /* Version C */
+#if (LWIP_CHKSUM_ALGORITHM == 3) /* Alternative version #3 */
 /**
  * An optimized checksum routine. Basically, it uses loop-unrolling on
  * the checksum loop, treating the head and tail bytes specially, whereas
@@ -236,8 +248,6 @@ lwip_standard_chksum(void *dataptr, int len)
 }
 #endif
 
-#endif /* LWIP_CHKSUM */
-
 /* inet_chksum_pseudo:
  *
  * Calculates the pseudo Internet checksum used by TCP and UDP for a pbuf chain.