+#ifdef CONFIG_TCP_MD5SIG
+/*
+ * Parse MD5 Signature option
+ */
+u8 *tcp_parse_md5sig_option(struct tcphdr *th)
+{
+ int length = (th->doff << 2) - sizeof (*th);
+ u8 *ptr = (u8*)(th + 1);
+
+ /* If the TCP option is too short, we can short cut */
+ if (length < TCPOLEN_MD5SIG)
+ return NULL;
+
+ while (length > 0) {
+ int opcode = *ptr++;
+ int opsize;
+
+ switch(opcode) {
+ case TCPOPT_EOL:
+ return NULL;
+ case TCPOPT_NOP:
+ length--;
+ continue;
+ default:
+ opsize = *ptr++;
+ if (opsize < 2 || opsize > length)
+ return NULL;
+ if (opcode == TCPOPT_MD5SIG)
+ return ptr;
+ }
+ ptr += opsize - 2;
+ length -= opsize;
+ }
+ return NULL;
+}
+#endif
+