Add missing frame.c

diff --git a/src/frame.c b/src/frame.c
new file mode 100644 (file)
index 0000000..a0ee59a
--- /dev/null
+++ b/src/frame.c
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2009 Vincent Bernat <bernat@luffy.cx>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "lldpd.h"
+
+u_int16_t
+frame_checksum(const u_char *cp, int len, int cisco)
+{
+       unsigned int sum = 0, v = 0;
+       int oddbyte = 0;
+
+       /* We compute in network byte order */
+       while ((len -= 2) >= 0) {
+               sum += *cp++ << 8;
+               sum += *cp++;
+       }
+       if ((oddbyte = len & 1) != 0)
+               v = *cp;
+
+       /* The remaining byte seems to be handled oddly by Cisco. Any hint about
+        * this is welcome. */
+       if (oddbyte) {
+               if (cisco)
+                       sum += v;
+               else
+                       sum += v << 8;
+       }
+       sum = (sum >> 16) + (sum & 0xffff);
+       sum += sum >> 16;
+       sum = ntohs(sum);
+       return (0xffff & ~sum);
+}