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Code Issues Releases Activity

Added PoC AS_PATH logic to BGP

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Pavel Odintsov 2024-07-14 19:01:12 +03:00
parent 5ed76a49ad
commit 742cbcae50
1 changed files with 166 additions and 24 deletions
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172
src/bgp_protocol.hpp
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@ -11,16 +11,12 @@
#include "dynamic_binary_buffer.hpp"
#include "fast_library.hpp"
#include "fastnetmon_networks.hpp"
#include "fast_endianless.hpp"
#include <boost/serialization/nvp.hpp>
#include "iana_ip_protocols.hpp"
#include "all_logcpp_libraries.hpp"
// Get log4cpp logger from main programme
extern log4cpp::Category& logger;
class bgp_attribute_origin;
class bgp_attribute_next_hop_ipv4;
class IPv4UnicastAnnounce;
@ -31,6 +27,8 @@ bool decode_bgp_subnet_encoding_ipv4(int len, uint8_t* value, subnet_cidr_mask_t
uint32_t how_much_bytes_we_need_for_storing_certain_subnet_mask(uint8_t prefix_bit_length);
std::string get_bgp_attribute_name_by_number(uint8_t bgp_attribute_type);
extern log4cpp::Category& logger;
enum BGP_PROTOCOL_MESSAGE_TYPES_UNTYPED : uint8_t {
BGP_PROTOCOL_MESSAGE_OPEN = 1,
BGP_PROTOCOL_MESSAGE_UPDATE = 2,
@ -245,16 +243,25 @@ enum EXTENDED_COMMUNITY_TYPES_LOW_FOR_COMMUNITY_TRANSITIVE_EXPEREMENTAL : uint8_
enum BGP_ATTRIBUTES_TYPES : uint8_t {
// https://www.ietf.org/rfc/rfc4271.txt from page 17
BGP_ATTRIBUTE_ORIGIN = 1,
BGP_ATTRIBUTE_AS_PATH = 2,
BGP_ATTRIBUTE_NEXT_HOP = 3,
BGP_ATTRIBUTE_MULTI_EXIT_DISC = 4,
BGP_ATTRIBUTE_LOCAL_PREF = 5,
BGP_ATTRIBUTE_ATOMIC_AGGREGATE = 6,
BGP_ATTRIBUTE_AGGREGATOR = 7,
// https://tools.ietf.org/html/rfc1997 from page 1
BGP_ATTRIBUTE_COMMUNITY = 8,
// https://tools.ietf.org/html/rfc4760 from page 2
BGP_ATTRIBUTE_MP_REACH_NLRI = 14,
// https://tools.ietf.org/html/rfc4360 from page 1
BGP_ATTRIBUTE_EXTENDED_COMMUNITY = 16,
};
@ -318,6 +325,54 @@ class __attribute__((__packed__)) bgp_attribute_community_t {
// Here we have multiple elements of type: bgp_community_attribute_element_t
};
// Format of AS_PATH element described here: https://www.rfc-editor.org/rfc/rfc4271.html#page-17
// And with 32 bit / 4 byte ASN corrections from here: https://www.rfc-editor.org/rfc/rfc6793 page 2
// The AS path information exchanged between NEW BGP speakers is carried in the existing AS_PATH attribute,
// except that each AS number in the attribute is encoded as a four-octet entity (instead of a two-octet entity).
class __attribute__((__packed__)) bgp_as_path_segment_element_t {
public:
// Path segment type declares on of two possible types of segments:
// 1 AS_SET: unordered set of ASes a route in the UPDATE message has traversed
// 2 AS_SEQUENCE: ordered set of ASes a route in the UPDATE message has traversed
// We use AS_SEQUENCE as default option
uint8_t path_segment_type = 2;
// The path segment length is a 1-octet length field, containing the number of ASes (not the number of octets) in
// the path segment value field.
uint8_t path_segment_length = 0;
// Here we store list of 4 byte ASNs encoded in 4 byte format each
};
// BGP attribute AS_PATH
// In RFC this encoding format is covered here: https://www.rfc-editor.org/rfc/rfc4271.html#page-18
class __attribute__((__packed__)) bgp_attribute_as_path_t {
public:
bgp_attribute_as_path_t() {
attribute_type = BGP_ATTRIBUTE_AS_PATH;
// Set attribute flags
attribute_flags.set_transitive_bit(true);
attribute_flags.set_partial_bit(false);
// It's mandatory: https://www.rfc-editor.org/rfc/rfc4271.html#section-5.1.2
attribute_flags.set_optional_bit(false);
// Means that we using single octet length field encoding:
// https://www.rfc-editor.org/rfc/rfc4271.html#page-17
attribute_flags.set_extended_length_bit(false);
}
bgp_attribute_flags attribute_flags;
uint8_t attribute_type = 0;
// This variable store total size in bytes of all AS_PATH elements
uint8_t attribute_length = 0;
// Here we have multiple elements of type: bgp_as_path_segment_element_t
};
// This is new extended communities:
// More details: https://tools.ietf.org/html/rfc4360
class __attribute__((__packed__)) bgp_extended_community_attribute_t {
@ -518,24 +573,81 @@ class IPv4UnicastAnnounce {
// origin_attr.print() <<
// std::endl;
dynamic_binary_buffer_t origin_as_binary_array;
origin_as_binary_array.set_maximum_buffer_size_in_bytes(sizeof(origin_attr));
origin_as_binary_array.append_data_as_object_ptr(&origin_attr);
bgp_attribute_next_hop_ipv4 next_hop_attr(next_hop);
// logger << log4cpp::Priority::WARN << "next_hop_attr: " <<
// next_hop_attr.print() <<
// std::endl;
dynamic_binary_buffer_t origin_as_binary_array;
origin_as_binary_array.set_maximum_buffer_size_in_bytes(sizeof(origin_attr));
origin_as_binary_array.append_data_as_object_ptr(&origin_attr);
dynamic_binary_buffer_t next_hop_as_binary_array;
next_hop_as_binary_array.set_maximum_buffer_size_in_bytes(sizeof(next_hop_attr));
next_hop_as_binary_array.append_data_as_object_ptr(&next_hop_attr);
// TODO: remove ugly code with custom build of each vector
if (community_list.empty()) {
// Vector should be ordered in ascending order of attribute types
return std::vector<dynamic_binary_buffer_t>{ origin_as_binary_array, next_hop_as_binary_array };
// Check numbers in enum BGP_ATTRIBUTES_TYPES for information
std::vector<dynamic_binary_buffer_t> attributes_list;
// It has attribute #1 and will be first in all the cases
attributes_list.push_back(origin_as_binary_array);
// AS Path should be here and it's #2
if (this->as_path_asns.size() > 0) {
// We have ASNs for AS_PATH attribute
bgp_attribute_as_path_t bgp_attribute_as_path;
// Populate attribute length
bgp_attribute_as_path.attribute_length =
sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t);
logger << log4cpp::Priority::DEBUG << "AS_PATH attribute length: " << uint32_t(bgp_attribute_as_path.attribute_length);
uint32_t as_path_attribute_full_length = sizeof(bgp_attribute_as_path_t) + bgp_attribute_as_path.attribute_length;
logger << log4cpp::Priority::DEBUG << "AS_PATH attribute full length: " << as_path_attribute_full_length;
dynamic_binary_buffer_t as_path_as_binary_array;
as_path_as_binary_array.set_maximum_buffer_size_in_bytes(as_path_attribute_full_length);
// Append attribute header
as_path_as_binary_array.append_data_as_object_ptr(&bgp_attribute_as_path);
bgp_as_path_segment_element_t bgp_as_path_segment_element;
// Numbers of ASNs in list
bgp_as_path_segment_element.path_segment_length = this->as_path_asns.size();
logger << log4cpp::Priority::DEBUG
<< "AS_PATH segments number: " << uint32_t(bgp_as_path_segment_element.path_segment_length);
// Append segment header
as_path_as_binary_array.append_data_as_object_ptr(&bgp_as_path_segment_element);
logger << log4cpp::Priority::DEBUG << "AS_PATH ASN numner: " << this->as_path_asns.size();
for (auto asn : this->as_path_asns) {
// Append all ASNs in big endian encoding
uint32_t asn_big_endian = fast_hton(asn);
as_path_as_binary_array.append_data_as_object_ptr(&asn_big_endian);
}
if (as_path_as_binary_array.is_failed()) {
logger << log4cpp::Priority::ERROR << "Issue with storing AS_PATH";
}
attributes_list.push_back(as_path_as_binary_array);
}
// Vector should be ordered in ascending order of attribute types
// Next hop attribute is #3
attributes_list.push_back(next_hop_as_binary_array);
if (community_list.empty()) {
return attributes_list;
} else {
// We have communities
bgp_attribute_community_t bgp_attribute_community;
@ -556,8 +668,10 @@ class IPv4UnicastAnnounce {
communities_list_as_binary_array.append_data_as_object_ptr(&bgp_community_element);
}
return std::vector<dynamic_binary_buffer_t>{ origin_as_binary_array, next_hop_as_binary_array,
communities_list_as_binary_array };
// Community is attribute #8
attributes_list.push_back(communities_list_as_binary_array);
return attributes_list;
}
}
@ -587,12 +701,25 @@ class IPv4UnicastAnnounce {
return true;
}
// Add ASN to AS_PATH
void add_asn_as_path(uint32_t asn) {
as_path_asns.push_back(asn);
}
// Sets AS_PATH to specified vector of uint32_t
void set_as_path(std::vector<uint32_t>& as_path_asns_param) {
as_path_asns = as_path_asns_param;
}
private:
uint32_t next_hop = 0;
subnet_cidr_mask_t prefix;
BGP_ORIGIN_TYPES origin = BGP_ORIGIN_INCOMPLETE;
bool is_withdraw = false;
std::vector<bgp_community_attribute_element_t> community_list;
// List of ASNs in 32 bit format. May be empty
std::vector<uint32_t> as_path_asns;
};
class IPv6UnicastAnnounce {
@ -663,12 +790,28 @@ class IPv6UnicastAnnounce {
return community_list;
}
// Add ASN to AS_PATH
void add_asn_as_path(uint32_t asn) {
as_path_asns.push_back(asn);
}
// Sets AS_PATH to specified vector of uint32_t
void set_as_path(std::vector<uint32_t>& as_path_asns_param) {
as_path_asns = as_path_asns_param;
}
private:
subnet_ipv6_cidr_mask_t next_hop{};
subnet_ipv6_cidr_mask_t prefix{};
BGP_ORIGIN_TYPES origin = BGP_ORIGIN_INCOMPLETE;
bool is_withdraw = false;
std::vector<bgp_community_attribute_element_t> community_list;
// TODO: we need to rework AnnounceUnicastPrefixLowLevelIPv6
// and pull all logic from it into get_attributes() right here
public:
// List of ASNs in 32 bit format. May be empty
std::vector<uint32_t> as_path_asns;
};
static_assert(sizeof(bgp_attribute_flags) == 1, "broken size for bgp_attribute_flags");
@ -686,4 +829,3 @@ bool encode_ipv6_announces_into_bgp_mp_reach_attribute(const IPv6UnicastAnnounce
dynamic_binary_buffer_t& bgp_mp_reach_ipv6_attribute);
bool encode_ipv6_prefix(const subnet_ipv6_cidr_mask_t& prefix, dynamic_binary_buffer_t& dynamic_buffer);