88 lines
2.4 KiB
C
Executable File
88 lines
2.4 KiB
C
Executable File
// SPDX-License-Identifier: LGPL-3.0-or-later
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/**
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* \file bgp/asn.h
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*
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* Types, constant and utilities to work with ASN of various width.
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*
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* \copyright The DoubleFourteen Code Forge (C) All Rights Reserved
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* \author Lorenzo Cogotti
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*/
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#ifndef DF_BGP_ASN_H_
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#define DF_BGP_ASN_H_
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#include "xpt.h"
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/// 2 octet `AS_TRANS` constant, in network order (big-endian).
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#define AS_TRANS BE16(23456)
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/// 4 octet `AS_TRANS` constant, in network order (big-endian).
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#define AS4_TRANS BE32(23456)
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/// 2 bytes wide AS number (ASN16), in network order (big-endian).
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typedef Uint16 Asn16;
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/// 4 bytes wide AS number (ASN32), in network order (big-endian).
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typedef Uint32 Asn32;
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/**
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* \brief Fat AS type capable of holding either a 4 octet (ASN32) or a 2 octet
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* (ASN16) AS number, with additional flags indicating ASN properties.
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*
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* \note This type doesn't reflect any actual BGP ASN encoding, it is merely
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* a convenience abstraction, useful when ASN properties should be bundled
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* with the actual ASN.
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*/
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typedef Sint64 Asn; // NOTE: signed so negative values may be used for
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// special purposes if necessary
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/// `Asn` flag indicating that the currently stored ASN is 4 octet wide (ASN32).
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#define ASN32BITFLAG BIT(62)
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/**
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* \brief Return an `Asn` holding an `Asn16` value.
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*
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* \note `asn` must be in network order (big endian).
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*/
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#define ASN16BIT(asn) ((Asn) ((Asn16) (asn)))
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/**
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* \brief Return an `Asn` holding a `Asn32`.
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*
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* \note `asn` should be in network order (big endian).
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*/
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#define ASN32BIT(asn) ((Asn) (ASN32BITFLAG | ((Asn) ((Asn32) asn))))
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/// Test whether an `Asn` is holding a 4 octet wide ASN.
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FORCE_INLINE Boolean ISASN32BIT(Asn asn)
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{
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return (asn & ASN32BITFLAG) != 0;
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}
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/**
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* \brief Extract AS number stored inside an `Asn`.
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*
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* Returned ASN is extended to `Asn32` even if it was originally an `Asn16`,
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* this allows code involving `Asn` to treat any ASN uniformly.
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*
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* \note Resulting ASN is in network byte order (big endian).
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*/
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FORCE_INLINE Asn32 ASN(Asn asn)
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{
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Asn32 res = asn & 0xffffffffuLL;
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#if EDN_NATIVE != EDN_BE
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// Shift _asn of 16 bits if this was originally ASN16,
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// on LE machines this mimics a BE16 word to BE32 dword extension
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res <<= (((asn & ASN32BITFLAG) == 0) << 4);
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#endif
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return res;
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}
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/// Test whether `asn` represents either `AS_TRANS` or `AS4_TRANS`.
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FORCE_INLINE Boolean ISASTRANS(Asn asn)
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{
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return ASN(asn) == AS4_TRANS;
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}
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#endif
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