Fix misleading RFC 5970 comment in bootfile-url handling

The previous comment incorrectly suggested that the Boot File URL option
in RFC 5970 limits the download protocol. While the RFC allows
various protocols, the current implementation only supports TFTP.

This patch updates the comment to clarify the current situation.

Fixes: tianocore#10742
Signed-off-by: Andreas Florath <[email protected]>

Author: florath

NetworkPkg/UefiPxeBcDxe/PxeBcDhcp6.c

@@ -415,10 +415,16 @@ PxeBcExtractBootFileUrl (
   //
 
   //
-  // Based upon RFC 5970 and UEFI 2.6, bootfile-url format can be
-  // tftp://[SERVER_ADDRESS]/BOOTFILE_NAME or tftp://domain_name/BOOTFILE_NAME
-  // As an example where the BOOTFILE_NAME is the EFI loader and
-  // SERVER_ADDRESS is the ASCII encoding of an IPV6 address.
+  // According to RFC 5970, the Boot File URL option does not restrict the
+  // download protocol, but only requires a valid URL. Although HTTP is
+  // recommended for network booting, the URL may also follow a TFTP-style
+  // format. This function expects URLs of the form:
+  //     protocol://[SERVER_ADDRESS]/BOOTFILE_NAME  or
+  //     protocol://domain_name/BOOTFILE_NAME
+  // where SERVER_ADDRESS is an ASCII-encoded IPv6 address and BOOTFILE_NAME
+  // typically denotes the EFI loader.
+  //
+  // Note: Currently, only the TFTP protocol is implemented.
   //
   PrefixLen = (UINT16)AsciiStrLen (PXEBC_DHCP6_BOOT_FILE_URL_PREFIX);