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bird/proto/babel/babel.h
Toke Høiland-Jørgensen d9763bd7a0
babel: Add route metric smoothing 
The Babel RTT extension employs metric smoothing to dampen route
oscillations in the face of varying RTT values between two peers[0].

This patch implements such dampening in Bird, roughly following the
implementation in babeld (i.e., using the same exponential function
definition). The main difference is that we calculate everything in the
native Bird microsecond time unit (and increase constants accordingly), and
that we split out the smoothed metric calculation in two function variants,
one that has no side effects and one that does.

  [0] https://arxiv.org/pdf/1403.3488.pdf

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
2022-12-12 13:46:36 +08:00

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/*
* BIRD -- The Babel protocol
*
* Copyright (c) 2015--2016 Toke Hoiland-Jorgensen
* (c) 2016--2017 Ondrej Zajicek <santiago@crfreenet.org>
* (c) 2016--2017 CZ.NIC z.s.p.o.
*
* Can be freely distributed and used under the terms of the GNU GPL.
*
* This file contains the data structures used by Babel.
*/
#ifndef _BIRD_BABEL_H_
#define _BIRD_BABEL_H_
#include "nest/bird.h"
#include "nest/cli.h"
#include "nest/iface.h"
#include "nest/route.h"
#include "nest/protocol.h"
#include "nest/locks.h"
#include "nest/password.h"
#include "lib/resource.h"
#include "lib/lists.h"
#include "lib/socket.h"
#include "lib/string.h"
#include "lib/timer.h"
#define EA_BABEL_METRIC EA_CODE(PROTOCOL_BABEL, 0)
#define EA_BABEL_ROUTER_ID EA_CODE(PROTOCOL_BABEL, 1)
#define EA_BABEL_SEQNO EA_CODE(PROTOCOL_BABEL, 2)
#define BABEL_MAGIC 42
#define BABEL_VERSION 2
#define BABEL_PORT 6696
#define BABEL_INFINITY 0xFFFF
#define BABEL_HELLO_INTERVAL_WIRED (4 S_) /* Default hello intervals in seconds */
#define BABEL_HELLO_INTERVAL_WIRELESS (4 S_)
#define BABEL_HELLO_LIMIT 12
#define BABEL_UPDATE_INTERVAL_FACTOR 4
#define BABEL_IHU_INTERVAL_FACTOR 3
#define BABEL_HOLD_TIME_FACTOR 4 /* How long we keep unreachable route relative to update interval */
#define BABEL_IHU_EXPIRY_FACTOR(X) ((btime)(X)*7/2) /* 3.5 */
#define BABEL_HELLO_EXPIRY_FACTOR(X) ((btime)(X)*3/2) /* 1.5 */
#define BABEL_ROUTE_EXPIRY_FACTOR(X) ((btime)(X)*7/2) /* 3.5 */
#define BABEL_ROUTE_REFRESH_FACTOR(X) ((btime)(X)*5/2) /* 2.5 */
#define BABEL_SEQNO_REQUEST_RETRY 4
#define BABEL_SEQNO_REQUEST_EXPIRY (2 S_)
#define BABEL_GARBAGE_INTERVAL (300 S_)
#define BABEL_RXCOST_WIRED 96
#define BABEL_RXCOST_WIRELESS 256
#define BABEL_RXCOST_RTT 96
#define BABEL_INITIAL_HOP_COUNT 255
#define BABEL_MAX_SEND_INTERVAL 5 /* Unused ? */
#define BABEL_INITIAL_NEIGHBOR_TIMEOUT (60 S_)
#define BABEL_RTT_MAX_VALUE (600 S_)
#define BABEL_RTT_MIN (10 MS_)
#define BABEL_RTT_MAX (120 MS_)
#define BABEL_RTT_DECAY 42
/*
* Constants for calculating metric smoothing. Chosen so that:
* log(2) = BABEL_SMOOTHING_CONSTANT / BABEL_SMOOTHING_UNIT, which means that
* log(2)/x can be calculated as BABEL_SMOOTHING_UNIT + BABEL_SMOOTHING_CONSTANT / x
*/
#define BABEL_SMOOTHING_UNIT 0x10000000
#define BABEL_SMOOTHING_CONSTANT 186065279
#define BABEL_SMOOTHING_STEP (1 S_) /* smoothing calculated in this step size */
#define BABEL_SMOOTHING_MIN_DIFF 4 /* metric diff beneath this is converged */
#define BABEL_SMOOTHING_DECAY (4 S_)
#define BABEL_SMOOTHING_DECAY_MAX (180 S_)
/* Max interval that will not overflow when carried as 16-bit centiseconds */
#define BABEL_TIME_UNITS 10000 /* On-wire times are counted in centiseconds */
#define BABEL_MIN_INTERVAL (0x0001 * BABEL_TIME_UNITS)
#define BABEL_MAX_INTERVAL (0xFFFF * BABEL_TIME_UNITS)
#define BABEL_OVERHEAD (IP6_HEADER_LENGTH+UDP_HEADER_LENGTH)
#define BABEL_MIN_MTU (512 + BABEL_OVERHEAD)
#define BABEL_AUTH_NONE 0
#define BABEL_AUTH_MAC 1
#define BABEL_AUTH_NONCE_LEN 10 /* we send 80 bit nonces */
#define BABEL_AUTH_MAX_NONCE_LEN 192 /* max allowed by spec */
#define BABEL_AUTH_INDEX_LEN 32 /* max size in spec */
#define BABEL_AUTH_CHALLENGE_TIMEOUT (30 S_)
#define BABEL_AUTH_CHALLENGE_INTERVAL (300 MS_) /* used for both challenges and replies */
enum babel_tlv_type {
BABEL_TLV_PAD1 = 0,
BABEL_TLV_PADN = 1,
BABEL_TLV_ACK_REQ = 2,
BABEL_TLV_ACK = 3,
BABEL_TLV_HELLO = 4,
BABEL_TLV_IHU = 5,
BABEL_TLV_ROUTER_ID = 6,
BABEL_TLV_NEXT_HOP = 7,
BABEL_TLV_UPDATE = 8,
BABEL_TLV_ROUTE_REQUEST = 9,
BABEL_TLV_SEQNO_REQUEST = 10,
BABEL_TLV_MAC = 16,
BABEL_TLV_PC = 17,
BABEL_TLV_CHALLENGE_REQUEST = 18,
BABEL_TLV_CHALLENGE_REPLY = 19,
BABEL_TLV_MAX
};
enum babel_subtlv_type {
BABEL_SUBTLV_PAD1 = 0,
BABEL_SUBTLV_PADN = 1,
BABEL_SUBTLV_DIVERSITY = 2, /* we don't support this */
BABEL_SUBTLV_TIMESTAMP = 3,
/* Mandatory subtlvs */
BABEL_SUBTLV_SOURCE_PREFIX = 128,
};
enum babel_iface_type {
/* In practice, UNDEF and WIRED give equivalent behaviour */
BABEL_IFACE_TYPE_UNDEF = 0,
BABEL_IFACE_TYPE_WIRED = 1,
BABEL_IFACE_TYPE_WIRELESS = 2,
BABEL_IFACE_TYPE_TUNNEL = 3,
BABEL_IFACE_TYPE_MAX
};
enum babel_ae_type {
BABEL_AE_WILDCARD = 0,
BABEL_AE_IP4 = 1,
BABEL_AE_IP6 = 2,
BABEL_AE_IP6_LL = 3,
BABEL_AE_MAX
};
struct babel_config {
struct proto_config c;
list iface_list; /* List of iface configs (struct babel_iface_config) */
btime metric_decay;
uint smooth_recp; /* Reciprocal for exponential metric smoothing */
uint hold_time; /* Time to hold stale entries and unreachable routes */
u8 randomize_router_id;
struct channel_config *ip4_channel;
struct channel_config *ip6_channel;
};
struct babel_iface_config {
struct iface_patt i;
u16 rxcost;
u8 type;
u8 limit; /* Minimum number of Hellos to keep link up */
u8 check_link;
uint port;
uint hello_interval; /* Hello interval, in us */
uint ihu_interval; /* IHU interval, in us */
uint update_interval; /* Update interval, in us */
btime rtt_min; /* rtt above which to start penalising metric */
btime rtt_max; /* max rtt metric penalty applied above this */
u16 rtt_cost; /* metric penalty to apply at rtt_max */
u16 rtt_decay; /* decay of neighbour RTT (units of 1/256) */
u8 rtt_send; /* whether to send timestamps on this interface */
u16 rx_buffer; /* RX buffer size, 0 for MTU */
u16 tx_length; /* TX packet length limit (including headers), 0 for MTU */
int tx_tos;
int tx_priority;
ip_addr next_hop_ip4;
ip_addr next_hop_ip6;
u8 auth_type; /* Authentication type (BABEL_AUTH_*) */
u8 auth_permissive; /* Don't drop packets failing auth check */
uint mac_num_keys; /* Number of configured HMAC keys */
uint mac_total_len; /* Total digest length for all configured keys */
list *passwords; /* Passwords for authentication */
};
struct babel_proto {
struct proto p;
timer *timer;
struct fib ip4_rtable;
struct fib ip6_rtable;
struct channel *ip4_channel;
struct channel *ip6_channel;
list interfaces; /* Interfaces we really know about (struct babel_iface) */
u64 router_id;
u16 update_seqno; /* To be increased on request */
u8 update_seqno_inc; /* Request for update_seqno increase */
u8 triggered; /* For triggering global updates */
slab *route_slab;
slab *source_slab;
slab *msg_slab;
slab *seqno_slab;
struct tbf log_pkt_tbf; /* TBF for packet messages */
};
struct babel_iface {
node n;
struct babel_proto *proto;
struct iface *iface;
struct babel_iface_config *cf;
u8 up;
pool *pool;
char *ifname;
sock *sk;
ip_addr addr;
ip_addr next_hop_ip4;
ip_addr next_hop_ip6;
int tx_length;
list neigh_list; /* List of neighbors seen on this iface (struct babel_neighbor) */
list msg_queue;
u16 hello_seqno; /* To be increased on each hello */
u32 auth_pc;
int auth_tx_overhead;
u8 auth_index[BABEL_AUTH_INDEX_LEN];
btime next_hello;
btime next_regular;
btime next_triggered;
btime want_triggered;
timer *timer;
event *send_event;
};
struct babel_neighbor {
node n;
struct babel_iface *ifa;
ip_addr addr;
u16 rxcost; /* Sent in last IHU */
u16 txcost; /* Received in last IHU */
u16 cost; /* Computed neighbor cost */
s8 ihu_cnt; /* IHU countdown, 0 to send it */
u8 hello_cnt;
u16 hello_map;
u16 next_hello_seqno;
uint last_hello_int;
u32 last_tstamp;
btime last_tstamp_rcvd;
btime srtt;
u32 auth_pc;
u8 auth_passed;
u8 auth_index_len;
u8 auth_index[BABEL_AUTH_INDEX_LEN];
u8 auth_nonce[BABEL_AUTH_NONCE_LEN];
btime auth_nonce_expiry;
btime auth_next_challenge;
btime auth_next_challenge_reply;
/* expiry timers */
btime hello_expiry;
btime ihu_expiry;
btime init_expiry;
list routes; /* Routes this neighbour has sent us (struct babel_route) */
list requests; /* Seqno requests bound to this neighbor */
};
struct babel_source {
node n;
u64 router_id;
u16 seqno;
u16 metric;
btime expires;
};
struct babel_route {
node n;
node neigh_route;
struct babel_entry *e;
struct babel_neighbor *neigh;
u8 feasible;
u16 seqno;
u16 metric;
u16 advert_metric;
u16 smoothed_metric;
u64 router_id;
ip_addr next_hop;
btime refresh_time;
btime smoothed_time;
btime expires;
};
struct babel_seqno_request {
node n;
node nbr_node;
u64 router_id;
u16 seqno;
u8 hop_count;
u8 count;
btime expires;
struct babel_neighbor *nbr;
};
struct babel_entry {
struct babel_route *selected;
list routes; /* Routes for this prefix (struct babel_route) */
list sources; /* Source entries for this prefix (struct babel_source). */
list requests;
u8 valid; /* Entry validity state (BABEL_ENTRY_*) */
u8 unreachable; /* Unreachable route is announced */
u16 seqno; /* Outgoing seqno */
u16 metric; /* Outgoing metric */
u64 router_id; /* Outgoing router ID */
btime updated; /* Last change of outgoing rte, for triggered updates */
struct fib_node n;
};
#define BABEL_ENTRY_DUMMY 0 /* No outgoing route */
#define BABEL_ENTRY_VALID 1 /* Valid outgoing route */
#define BABEL_ENTRY_STALE 2 /* Stale outgoing route, waiting for GC */
/*
* Internal TLV messages
*/
struct babel_msg_ack_req {
u8 type;
u16 nonce;
uint interval;
ip_addr sender;
};
struct babel_msg_ack {
u8 type;
u16 nonce;
};
struct babel_msg_hello {
u8 type;
u16 seqno;
uint interval;
ip_addr sender;
u32 tstamp;
btime pkt_received;
};
struct babel_msg_ihu {
u8 type;
u8 ae;
u16 rxcost;
uint interval;
ip_addr addr;
ip_addr sender;
u32 tstamp;
u32 tstamp_rcvd;
btime pkt_received;
};
struct babel_msg_update {
u8 type;
u8 wildcard;
uint interval;
u16 seqno;
u16 metric;
u64 router_id;
union {
net_addr net;
net_addr_ip6_sadr net_sadr;
};
ip_addr next_hop;
ip_addr sender;
};
struct babel_msg_route_request {
u8 type;
u8 full;
union {
net_addr net;
net_addr_ip6_sadr net_sadr;
};
};
struct babel_msg_seqno_request {
u8 type;
u8 hop_count;
u16 seqno;
u64 router_id;
union {
net_addr net;
net_addr_ip6_sadr net_sadr;
};
ip_addr sender;
};
struct babel_msg_challenge {
u8 type;
u8 nonce_len;
u8 *nonce;
};
union babel_msg {
u8 type;
struct babel_msg_ack_req ack_req;
struct babel_msg_ack ack;
struct babel_msg_hello hello;
struct babel_msg_ihu ihu;
struct babel_msg_update update;
struct babel_msg_route_request route_request;
struct babel_msg_seqno_request seqno_request;
struct babel_msg_challenge challenge;
};
struct babel_msg_node {
node n;
union babel_msg msg;
};
/* only used for auth checking, so not a part of union above */
struct babel_msg_auth {
ip_addr sender;
u32 pc;
u8 pc_seen;
u8 index_len;
u8 *index;
u8 challenge_reply_seen;
u8 challenge_reply[BABEL_AUTH_NONCE_LEN];
u8 challenge_seen;
u8 challenge_len;
u8 challenge[BABEL_AUTH_MAX_NONCE_LEN];
};
static inline int babel_sadr_enabled(struct babel_proto *p)
{ return p->ip6_rtable.addr_type == NET_IP6_SADR; }
/* babel.c */
void babel_handle_ack_req(union babel_msg *msg, struct babel_iface *ifa);
void babel_handle_ack(union babel_msg *msg, struct babel_iface *ifa);
void babel_handle_hello(union babel_msg *msg, struct babel_iface *ifa);
void babel_handle_ihu(union babel_msg *msg, struct babel_iface *ifa);
void babel_handle_router_id(union babel_msg *msg, struct babel_iface *ifa);
void babel_handle_update(union babel_msg *msg, struct babel_iface *ifa);
void babel_handle_route_request(union babel_msg *msg, struct babel_iface *ifa);
void babel_handle_seqno_request(union babel_msg *msg, struct babel_iface *ifa);
void babel_show_interfaces(struct proto *P, const char *iff);
void babel_show_neighbors(struct proto *P, const char *iff);
void babel_show_entries(struct proto *P);
void babel_show_routes(struct proto *P);
void babel_auth_reset_index(struct babel_iface *ifa);
int babel_auth_check_pc(struct babel_iface *ifa, struct babel_msg_auth *msg);
/* packets.c */
void babel_enqueue(union babel_msg *msg, struct babel_iface *ifa);
void babel_send_unicast(union babel_msg *msg, struct babel_iface *ifa, ip_addr dest);
int babel_open_socket(struct babel_iface *ifa);
void babel_send_queue(void *arg);
void babel_auth_set_tx_overhead(struct babel_iface *ifa);
#endif
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