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icmp: clean up the extension code and comments.

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Remove remaining references to them as being MPLS-related;
draft-bonica-icmp-mpls-02 referred to them as "ICMP Extensions for
MultiProtocol Label Switching", but draft-bonica-internet-icmp-00
redefined it as a general extension mechanism, not MPLS-related, and
that draft eventually became RFC 4884.

draft-bonica-icmp-mpls-02 also defined class 2 objects as objects
containing the remaining packet information past the first 128 bytes;
that never became part of an RFC and class 2 was redefined as an
"Interface Information Object" in RFC 5837.

Give some of these details in comments, and move some
extension-related definitions among the rest of the extension stuff.
This commit is contained in:
Guy Harris 2022-03-19 22:17:43 -07:00
parent 0bf5c3360d
commit 6d3b0e4599
1 changed files with 34 additions and 12 deletions
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46
print-icmp.c
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@ -86,9 +86,6 @@ struct icmp {
#define icmp_data icmp_dun.id_data
};
#define ICMP_EXT_EXTRACT_VERSION(x) (((x)&0xf0)>>4)
#define ICMP_MPLS_EXT_VERSION 2
/*
* Lower bounds on packet lengths for various types.
* For the error advice packets must first insure that the
@ -188,11 +185,6 @@ struct icmp {
#define ICMP_UNREACH_PRECEDENCE_CUTOFF 15 /* precedence cutoff */
#endif
/* rfc4950 */
#define MPLS_STACK_ENTRY_OBJECT_CLASS 1
/* rfc5837 */
#define INTERFACE_INFORMATION_OBJECT_CLASS 2
/* Most of the icmp types */
static const struct tok icmp2str[] = {
{ ICMP_ECHOREPLY, "echo reply" },
@ -226,13 +218,17 @@ struct id_rdiscovery {
};
/*
* draft-bonica-internet-icmp-08
* RFC 4884 - Extended ICMP to Support Multi-Part Messages
*
* This is a general extension mechanism, based on the mechanism
* in draft-bonica-icmp-mpls-02 ICMP Extensions for MultiProtocol
* Label Switching.
*
* The Destination Unreachable, Time Exceeded
* and Parameter Problem messages are slightly changed as per
* the above draft. A new Length field gets added to give
* the above RFC. A new Length field gets added to give
* the caller an idea about the length of the piggybacked
* IP packet before the MPLS extension header starts.
* IP packet before the extension header starts.
*
* The Length field represents length of the padded "original datagram"
* field measured in 32-bit words.
@ -264,6 +260,32 @@ struct icmp_ext_t {
nd_byte icmp_ext_data[1];
};
/*
* Extract version from the first octet of icmp_ext_version_res.
*/
#define ICMP_EXT_EXTRACT_VERSION(x) (((x)&0xf0)>>4)
/*
* Current version.
*/
#define ICMP_EXT_VERSION 2
/*
* Extension object class numbers.
*
* Class 1 dates back to draft-bonica-icmp-mpls-02.
*
* Class 2 was used for an "Extended Payload Object Class", which
* contained bytes of the payload beyond the first 128 bytes, in
* draft-bonica-icmp-mpls-02; it was reassigned to an "Interface
* Information Object" in RFC 5837.
*/
/* rfc4950 */
#define MPLS_STACK_ENTRY_OBJECT_CLASS 1
/* rfc5837 */
#define INTERFACE_INFORMATION_OBJECT_CLASS 2
struct icmp_multipart_ext_object_header_t {
nd_uint16_t length;
nd_uint8_t class_num;
@ -748,7 +770,7 @@ icmp_print(netdissect_options *ndo, const u_char *bp, u_int plen, const u_char *
* Sanity checking of the header.
*/
if (ICMP_EXT_EXTRACT_VERSION(*(ext_dp->icmp_ext_version_res)) !=
ICMP_MPLS_EXT_VERSION) {
ICMP_EXT_VERSION) {
ND_PRINT(" packet not supported");
return;
}