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-rw-r--r--lib/Modules2
-rw-r--r--lib/checksum.c59
-rw-r--r--lib/checksum.h20
3 files changed, 81 insertions, 0 deletions
diff --git a/lib/Modules b/lib/Modules
index 19a7900..1597b9a 100644
--- a/lib/Modules
+++ b/lib/Modules
@@ -27,3 +27,5 @@ slists.c
slists.h
event.c
event.h
+checksum.c
+checksum.h
diff --git a/lib/checksum.c b/lib/checksum.c
new file mode 100644
index 0000000..4dfa252
--- /dev/null
+++ b/lib/checksum.c
@@ -0,0 +1,59 @@
+/*
+ * BIRD Library -- IP One-Complement Checksum
+ *
+ * (c) 1999 Martin Mares <mj@ucw.cz>
+ *
+ * Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#include <stdarg.h>
+
+#include "nest/bird.h"
+#include "checksum.h"
+
+static u16
+ipsum_calc(void *frag, unsigned len, va_list args)
+{
+ u16 sum = 0;
+
+ for(;;)
+ {
+ u16 *x = frag;
+ ASSERT(!(len % 2));
+ while (len)
+ {
+ u16 z = sum + *x++;
+ sum = z + (z < sum);
+ len -= 2;
+ }
+ frag = va_arg(args, void *);
+ if (!frag)
+ break;
+ len = va_arg(args, unsigned);
+ }
+ return sum;
+}
+
+int
+ipsum_verify(void *frag, unsigned len, ...)
+{
+ va_list args;
+ u16 sum;
+
+ va_start(args, len);
+ sum = ipsum_calc(frag, len, args);
+ va_end(args);
+ return sum == 0xffff;
+}
+
+u16
+ipsum_calculate(void *frag, unsigned len, ...)
+{
+ va_list args;
+ u16 sum;
+
+ va_start(args, len);
+ sum = ipsum_calc(frag, len, args);
+ va_end(args);
+ return 0xffff - sum;
+}
diff --git a/lib/checksum.h b/lib/checksum.h
new file mode 100644
index 0000000..8151554
--- /dev/null
+++ b/lib/checksum.h
@@ -0,0 +1,20 @@
+/*
+ * BIRD Library -- IP One-Complement Checksum
+ *
+ * (c) 1999 Martin Mares <mj@ucw.cz>
+ *
+ * Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#ifndef _BIRD_CHECKSUM_H_
+#define _BIRD_CHECKSUM_H_
+
+/*
+ * Both checksumming functions accept a vararg list of packet
+ * fragments finished by NULL pointer.
+ */
+
+int ipsum_verify(void *frag, unsigned len, ...);
+u16 ipsum_calculate(void *frag, unsigned len, ...);
+
+#endif