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serval-dna/route_link.c

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#include "serval.h"
#include "overlay_address.h"
#include "overlay_buffer.h"
#include "overlay_packet.h"
#include "str.h"
#include "conf.h"
/*
Link state routing;
- each node sends a packet on a heartbeat
- on recieving a packet, update a link cost calculation (initially up/down only)
- when the cost changes, update a version field
- every heartbeat interval, send link cost details
- send link cost for every neighbour, they need to know we can still hear them.
- after parsing incoming link details, if anything has changed, mark routes as dirty
*/
#define INCLUDE_ANYWAY (500)
#define MAX_LINK_STATES 512
#define FLAG_HAS_INTERFACE (1<<0)
#define FLAG_NO_PATH (1<<1)
#define FLAG_BROADCAST (1<<2)
#define FLAG_UNICAST (1<<3)
#define FLAG_HAS_ACK (1<<4)
#define FLAG_HAS_DROP_RATE (1<<5)
#define ACK_WINDOW (16)
struct link{
struct link *_left;
struct link *_right;
struct subscriber *transmitter;
struct link *parent;
struct overlay_interface *interface;
struct subscriber *receiver;
// neighbour path version when path scores were last updated
char path_version;
// link quality stats;
char link_version;
char drop_rate;
// calculated path score;
int hop_count;
int path_drop_rate;
// loop prevention;
char calculating;
};
struct neighbour_link{
struct neighbour_link *_next;
// which of their interfaces are these stats for?
int neighbour_interface;
// which interface did we hear it on?
struct overlay_interface *interface;
// very simple time based link up/down detection;
// when will we consider the link broken?
time_ms_t link_timeout;
char unicast;
int ack_sequence;
uint32_t ack_mask;
};
struct neighbour{
struct neighbour *_next;
struct subscriber *subscriber;
// whenever we hear about a link change, update the version to mark all link path scores as dirty
char path_version;
// when do we assume the link is dead because they stopped hearing us or vice versa?
time_ms_t neighbour_link_timeout;
// next link update
time_ms_t next_neighbour_update;
int ack_counter;
// un-balanced tree of known link states
struct link *root;
// list of incoming link stats
struct neighbour_link *links, *best_link;
};
// one struct per subscriber, where we track all routing information, allocated on first use
struct link_state{
// what is the current best hop count? (via subscriber->next_hop)
struct subscriber *next_hop;
struct subscriber *transmitter;
int hop_count;
int route_version;
// if a neighbour is free'd this link will point to invalid memory.
// do not trust this pointer unless you have just called find_best_link
struct link *link;
char calculating;
// when do we need to send a new link state message.
time_ms_t next_update;
};
static void link_send(struct sched_ent *alarm);
static struct profile_total link_send_stats={
.name="link_send",
};
static struct sched_ent link_send_alarm={
.function = link_send,
.stats = &link_send_stats,
};
struct neighbour *neighbours=NULL;
int route_version=0;
static int NumberOfSetBits(uint32_t i)
{
i = i - ((i >> 1) & 0x55555555);
i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
return (((i + (i >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
}
static struct link_state *get_link_state(struct subscriber *subscriber)
{
if (!subscriber->link_state){
subscriber->link_state = emalloc_zero(sizeof(struct link_state));
subscriber->link_state->route_version = route_version -1;
}
return subscriber->link_state;
}
static struct neighbour *get_neighbour(struct subscriber *subscriber, char create)
{
struct neighbour *n = neighbours;
while(n){
if (n->subscriber==subscriber)
return n;
n = n->_next;
}
if (create){
n = emalloc_zero(sizeof(struct neighbour));
n->subscriber = subscriber;
n->_next = neighbours;
neighbours = n;
if (config.debug.linkstate)
DEBUGF("LINK STATE; new neighbour %s", alloca_tohex_sid(n->subscriber->sid));
}
return n;
}
static void free_links(struct link *link)
{
if (!link)
return;
free_links(link->_left);
link->_left=NULL;
free_links(link->_right);
link->_right=NULL;
free(link);
}
static struct link *find_link(struct neighbour *neighbour, struct subscriber *receiver, char create)
{
struct link **link_ptr=&neighbour->root, *link=neighbour->root;
while(1){
if (link==NULL){
if (create){
link = *link_ptr = emalloc_zero(sizeof(struct link));
link->receiver = receiver;
link->path_version = neighbour->path_version -1;
}
break;
}
if (receiver == link->receiver)
break;
if (memcmp(receiver->sid, link->receiver->sid, SID_SIZE)<0){
link_ptr = &link->_left;
}else{
link_ptr = &link->_right;
}
link = *link_ptr;
}
return link;
}
static struct link *get_parent(struct neighbour *neighbour, struct link *link)
{
// root of the routing table.
if (link->receiver == neighbour->subscriber || link->transmitter == NULL)
return NULL;
if (!link->parent)
link->parent = find_link(neighbour, link->transmitter, 0);
return link->parent;
}
static void update_path_score(struct neighbour *neighbour, struct link *link){
if (link->path_version == neighbour->path_version)
return;
if (link->calculating)
return;
link->calculating = 1;
int hop_count = -1;
int drop_rate = 0;
if (link->transmitter == my_subscriber){
if (link->receiver==neighbour->subscriber){
hop_count = 1;
}
}else{
struct link *parent = get_parent(neighbour, link);
if (parent && (!parent->calculating)){
update_path_score(neighbour, parent);
// TODO more interesting path cost metrics...
if (parent->hop_count>0){
hop_count = parent->hop_count+1;
drop_rate = parent->path_drop_rate;
}
}
}
// ignore occasional dropped packets due to collisions
if (link->drop_rate>2)
drop_rate += link->drop_rate;
if (config.debug.verbose && config.debug.linkstate && hop_count != link->hop_count)
DEBUGF("LINK STATE; path score to %s via %s version %d = %d",
alloca_tohex_sid(link->receiver->sid),
alloca_tohex_sid(neighbour->subscriber->sid),
neighbour->path_version,
hop_count);
link->hop_count = hop_count;
link->path_version = neighbour->path_version;
link->path_drop_rate = drop_rate;
link->calculating = 0;
}
static int find_best_link(struct subscriber *subscriber)
{
if (subscriber->reachable==REACHABLE_SELF)
return 0;
struct link_state *state = get_link_state(subscriber);
if (state->route_version == route_version)
return 0;
if (state->calculating)
return -1;
state->calculating = 1;
struct neighbour *neighbour = neighbours;
struct overlay_interface *interface = NULL;
int best_hop_count = 99;
int best_drop_rate = 99;
struct link *best_link = NULL;
struct subscriber *next_hop = NULL, *transmitter=NULL;
time_ms_t now = gettime_ms();
while (neighbour){
if (neighbour->neighbour_link_timeout < now)
goto next;
struct link *link = find_link(neighbour, subscriber, 0);
if (!(link && link->transmitter))
goto next;
if (link->transmitter != my_subscriber){
struct link_state *parent_state = get_link_state(link->transmitter);
find_best_link(link->transmitter);
if (parent_state->next_hop != neighbour->subscriber)
goto next;
}
update_path_score(neighbour, link);
if (link->hop_count>0){
if (link->path_drop_rate < best_drop_rate ||
(link->path_drop_rate == best_drop_rate && link->hop_count < best_hop_count)){
next_hop = neighbour->subscriber;
best_hop_count = link->hop_count;
best_drop_rate = link->path_drop_rate;
transmitter = link->transmitter;
interface = link->interface;
best_link = link;
}
}
next:
neighbour = neighbour->_next;
}
int changed =0;
if (state->next_hop != next_hop || state->transmitter != transmitter || state->link != best_link)
changed = 1;
if (next_hop == subscriber && (interface != subscriber->interface))
changed = 1;
state->next_hop = next_hop;
state->transmitter = transmitter;
state->hop_count = best_hop_count;
state->route_version = route_version;
state->calculating = 0;
state->link = best_link;
int reachable = subscriber->reachable;
if (next_hop == NULL){
if (!(subscriber->reachable & REACHABLE_ASSUMED))
reachable = REACHABLE_NONE;
} else if (next_hop == subscriber){
// reset the state of any unicast probe's if the interface has changed
if (subscriber->interface != interface){
reachable = 0;
subscriber->last_probe=0;
bzero(&subscriber->address, sizeof subscriber->address);
}
reachable = REACHABLE_BROADCAST | (subscriber->reachable & REACHABLE_UNICAST);
subscriber->interface = interface;
} else {
reachable = REACHABLE_INDIRECT;
}
subscriber->next_hop = next_hop;
set_reachable(subscriber, reachable);
if (changed){
if (config.debug.linkstate){
if (next_hop == subscriber){
DEBUGF("LINK STATE; neighbour %s is reachable on interface %s",
alloca_tohex_sid(subscriber->sid),
interface->name);
} else {
DEBUGF("LINK STATE; next hop for %s is now %d hops, %s via %s",
alloca_tohex_sid(subscriber->sid),
best_hop_count,
next_hop?alloca_tohex_sid(next_hop->sid):"UNREACHABLE",
transmitter?alloca_tohex_sid(transmitter->sid):"NONE");
}
}
monitor_announce_link(best_hop_count, transmitter, subscriber);
state->next_update = now;
}
return 0;
}
static int monitor_announce(struct subscriber *subscriber, void *context){
if (subscriber->reachable & REACHABLE){
struct link_state *state = get_link_state(subscriber);
monitor_announce_link(state->hop_count, state->transmitter, subscriber);
}
return 0;
}
int link_state_announce_links(){
enum_subscribers(NULL, monitor_announce, NULL);
return 0;
}
static int append_link_state(struct overlay_buffer *payload, char flags,
struct subscriber *transmitter, struct subscriber *receiver,
int interface, int version, int ack_sequence, uint32_t ack_mask,
int drop_rate)
{
if (interface!=-1)
flags|=FLAG_HAS_INTERFACE;
if (!transmitter)
flags|=FLAG_NO_PATH;
if (ack_sequence!=-1)
flags|=FLAG_HAS_ACK;
if (drop_rate!=-1)
flags|=FLAG_HAS_DROP_RATE;
int length_pos = ob_position(payload);
if (ob_append_byte(payload, 0))
return -1;
if (ob_append_byte(payload, flags))
return -1;
if (overlay_address_append(NULL, payload, receiver))
return -1;
if (ob_append_byte(payload, version))
return -1;
if (transmitter)
if (overlay_address_append(NULL, payload, transmitter))
return -1;
if (interface!=-1)
if (ob_append_byte(payload, interface))
return -1;
if (ack_sequence!=-1){
if (ob_append_byte(payload, ack_sequence))
return -1;
if (ob_append_ui32(payload, ack_mask))
return -1;
}
if (drop_rate!=-1)
if (ob_append_byte(payload, drop_rate))
return -1;
// TODO insert future fields here
// patch the record length
int end_pos = ob_position(payload);
if (ob_set(payload, length_pos, end_pos - length_pos))
return -1;
ob_checkpoint(payload);
return 0;
}
static int append_link(struct subscriber *subscriber, void *context)
{
if (subscriber == my_subscriber)
return 0;
struct overlay_buffer *payload = context;
struct link_state *state = get_link_state(subscriber);
time_ms_t now = gettime_ms();
if (find_best_link(subscriber))
return 0;
if (state->next_update - INCLUDE_ANYWAY <= now){
if (subscriber->reachable==REACHABLE_SELF){
// Other entries in our keyring are always one hop away from us.
if (append_link_state(payload, 0, my_subscriber, subscriber, -1, 1, -1, 0, 0)){
link_send_alarm.alarm = now;
return 1;
}
} else {
struct link *link = state->link;
if (append_link_state(payload, 0, state->transmitter, subscriber, -1, link?link->link_version:-1, -1, 0, link?link->drop_rate:32)){
link_send_alarm.alarm = now;
return 1;
}
}
// include information about this link every 5s
state->next_update = now + 5000;
}
if (state->next_update < link_send_alarm.alarm)
link_send_alarm.alarm = state->next_update;
return 0;
}
static void free_neighbour(struct neighbour **neighbour_ptr){
struct neighbour *n = *neighbour_ptr;
if (config.debug.linkstate && config.debug.verbose)
DEBUGF("LINK STATE; all links from neighbour %s have died", alloca_tohex_sid(n->subscriber->sid));
struct neighbour_link *link = n->links;
while(link){
struct neighbour_link *l=link;
link = l->_next;
free(l);
}
free_links(n->root);
n->root=NULL;
*neighbour_ptr = n->_next;
free(n);
route_version++;
}
static void clean_neighbours(time_ms_t now)
{
struct neighbour **n_ptr = &neighbours;
while (*n_ptr){
struct neighbour *n = *n_ptr;
struct neighbour_link **list = &n->links;
while(*list){
struct neighbour_link *link = *list;
if (link->interface->state!=INTERFACE_STATE_UP || link->link_timeout < now){
if (config.debug.linkstate && config.debug.verbose)
DEBUGF("LINK STATE; link expired from neighbour %s on interface %s",
alloca_tohex_sid(n->subscriber->sid),
link->interface->name);
*list=link->_next;
free(link);
}else{
list = &link->_next;
}
}
if (!n->links){
free_neighbour(n_ptr);
}else{
n_ptr = &n->_next;
}
}
}
static int link_send_neighbours(struct overlay_buffer *payload)
{
time_ms_t now = gettime_ms();
clean_neighbours(now);
struct neighbour *n = neighbours;
while (n){
// TODO compare other link stats to find the best...
struct neighbour_link *best_link=n->links;
if (best_link){
struct neighbour_link *link=best_link->_next;
while(link){
if (link->interface != best_link->interface &&
overlay_interface_compare(best_link->interface, link->interface))
best_link = link;
link = link->_next;
}
}
if (n->best_link != best_link){
n->best_link = best_link;
n->next_neighbour_update = now;
if (config.debug.linkstate && config.debug.verbose)
DEBUGF("LINK STATE; best link from neighbour %s is now on interface %s",
alloca_tohex_sid(n->subscriber->sid),
best_link?best_link->interface->name:"NONE");
}
char flags=0;
if (best_link->unicast)
flags|=FLAG_UNICAST;
else
flags|=FLAG_BROADCAST;
if (n->next_neighbour_update - INCLUDE_ANYWAY <= now){
if (append_link_state(payload, flags, n->subscriber, my_subscriber, best_link->neighbour_interface, 1, best_link->ack_sequence, best_link->ack_mask, -1)){
link_send_alarm.alarm = now;
return 1;
}
n->next_neighbour_update = now + best_link->interface->tick_ms;
n->ack_counter = ACK_WINDOW;
}
if (n->next_neighbour_update < link_send_alarm.alarm)
link_send_alarm.alarm = n->next_neighbour_update;
n = n->_next;
}
return 0;
}
// send link details
static void link_send(struct sched_ent *alarm)
{
time_ms_t now = gettime_ms();
alarm->alarm=now + 10000;
struct overlay_frame *frame=emalloc_zero(sizeof(struct overlay_frame));
frame->type=OF_TYPE_DATA;
frame->source=my_subscriber;
frame->ttl=1;
frame->queue=OQ_MESH_MANAGEMENT;
frame->payload = ob_new();
ob_limitsize(frame->payload, 400);
overlay_mdp_encode_ports(frame->payload, MDP_PORT_LINKSTATE, MDP_PORT_LINKSTATE);
ob_checkpoint(frame->payload);
int pos = ob_position(frame->payload);
if (link_send_neighbours(frame->payload)==0){
enum_subscribers(NULL, append_link, frame->payload);
}
ob_rewind(frame->payload);
if (ob_position(frame->payload) == pos)
op_free(frame);
else if (overlay_payload_enqueue(frame))
op_free(frame);
alarm->deadline = alarm->alarm;
schedule(alarm);
}
static void update_alarm(time_ms_t limit){
if (link_send_alarm.alarm>limit || link_send_alarm.alarm==0){
unschedule(&link_send_alarm);
link_send_alarm.alarm = limit;
link_send_alarm.deadline = limit+10;
schedule(&link_send_alarm);
}
}
struct neighbour_link * get_neighbour_link(struct neighbour *neighbour, struct overlay_interface *interface, int sender_interface, char unicast)
{
struct neighbour_link *link = neighbour->links;
while(link){
if (link->interface == interface && link->neighbour_interface == sender_interface && link->unicast == unicast)
return link;
link=link->_next;
}
link = emalloc_zero(sizeof(struct neighbour_link));
link->interface = interface;
link->neighbour_interface = sender_interface;
link->unicast = unicast;
link->ack_sequence = -1;
link->ack_mask = 0;
link->_next = neighbour->links;
if (config.debug.linkstate && config.debug.verbose)
DEBUGF("LINK STATE; new possible link from neighbour %s on interface %s/%d",
alloca_tohex_sid(neighbour->subscriber->sid),
interface->name,
sender_interface);
neighbour->links = link;
return link;
}
// track stats for receiving packets from this neighbour
int link_received_packet(struct subscriber *subscriber, struct overlay_interface *interface, int sender_interface, int sender_seq, int unicast)
{
// TODO better handling of unicast routes
if (unicast)
return 0;
struct neighbour *neighbour = get_neighbour(subscriber, 1);
struct neighbour_link *link=get_neighbour_link(neighbour, interface, sender_interface, unicast);
time_ms_t now = gettime_ms();
time_ms_t next_update = neighbour->next_neighbour_update;
neighbour->ack_counter --;
// for now we'll use a simple time based link up/down flag
if (sender_seq >=0){
if (link->ack_sequence != -1){
int offset = (link->ack_sequence - 1 - sender_seq)&0xFF;
if (offset < 32){
if (config.debug.verbose && config.debug.linkstate)
DEBUGF("LINK STATE; late seq %d from %s on %s",
sender_seq, alloca_tohex_sid(subscriber->sid), interface->name);
link->ack_mask |= (1<<offset);
}else{
link->ack_mask = (link->ack_mask << 1) | 1;
while(1){
link->ack_sequence = (link->ack_sequence+1)&0xFF;
if (link->ack_sequence == sender_seq)
break;
// missed a packet? send a link state soon
if (config.debug.verbose && config.debug.linkstate)
DEBUGF("LINK STATE; missed seq %d from %s on %s",
link->ack_sequence, alloca_tohex_sid(subscriber->sid), interface->name);
link->ack_mask = link->ack_mask << 1;
next_update = now+100;
}
}
}else
link->ack_sequence = sender_seq;
}
// force an update soon when we need to ack packets
if (neighbour->ack_counter <=0)
next_update = now+10;
// force an update when we start hearing a new neighbour link
if (link->link_timeout < now)
next_update = now;
if (next_update < neighbour->next_neighbour_update){
neighbour->next_neighbour_update = next_update;
}
update_alarm(neighbour->next_neighbour_update);
link->link_timeout = now + (interface->tick_ms *5);
return 0;
}
// parse incoming link details
int link_receive(overlay_mdp_frame *mdp)
{
struct overlay_buffer *payload = ob_static(mdp->out.payload, mdp->out.payload_length);
ob_limitsize(payload, mdp->out.payload_length);
struct subscriber *sender = find_subscriber(mdp->out.src.sid, SID_SIZE, 0);
struct neighbour *neighbour = get_neighbour(sender, 1);
struct decode_context context;
bzero(&context, sizeof(context));
time_ms_t now = gettime_ms();
char changed = 0;
while(ob_remaining(payload)>0){
context.invalid_addresses=0;
struct subscriber *receiver=NULL, *transmitter=NULL;
struct overlay_interface *interface = NULL;
int start_pos = ob_position(payload);
int length = ob_get(payload);
if (length <=0)
break;
int flags = ob_get(payload);
if (flags<0)
break;
if (overlay_address_parse(&context, payload, &receiver))
break;
int version = ob_get(payload);
if (version < 0)
break;
if (!(flags & FLAG_NO_PATH)){
if (overlay_address_parse(&context, payload, &transmitter))
break;
}
int interface_id = -1;
if (flags & FLAG_HAS_INTERFACE){
interface_id = ob_get(payload);
if (interface_id < 0)
break;
if (interface_id >= OVERLAY_MAX_INTERFACES)
continue;
}
int ack_seq = -1;
uint32_t ack_mask = 0;
int drop_rate = -1;
if (flags & FLAG_HAS_ACK){
ack_seq = ob_get(payload);
ack_mask = ob_get_ui32(payload);
drop_rate = 15 - NumberOfSetBits((ack_mask & 0x7FFF));
// we can deal with low packet loss, it's not interesting if it changes, ignore it.
if (drop_rate <=2)
drop_rate = 0;
}
if (flags & FLAG_HAS_DROP_RATE){
drop_rate = ob_get(payload);
if (drop_rate <0)
break;
}
// jump to the position of the next record, even if there's more data we don't understand
payload->position = start_pos + length;
if (context.invalid_addresses)
continue;
// ignore any links that our neighbour is using to route through us.
if (receiver == my_subscriber)
continue;
if (receiver == sender){
// who can our neighbour hear?
// TODO build a map of everyone in our 2 hop neighbourhood to control broadcast flooding?
if (transmitter == my_subscriber && interface_id != -1){
// TODO get matching neighbour link and combine scores
// TODO use ack_sequence && ack_mask to control (re)sending packets
// they can hear us? we can route through them!
interface = &overlay_interfaces[interface_id];
if (interface->state != INTERFACE_STATE_UP)
continue;
if (neighbour->neighbour_link_timeout < now)
changed = 1;
neighbour->neighbour_link_timeout = now + interface->tick_ms * 5;
}else
continue;
}else if(transmitter == my_subscriber)
transmitter = NULL;
struct link *link = find_link(neighbour, receiver, transmitter?1:0);
if (link && transmitter == my_subscriber){
// TODO combine our link stats with theirs
version = link->link_version;
if (drop_rate != link->drop_rate)
version++;
}
if (link && (link->transmitter != transmitter || link->link_version != version)){
changed = 1;
link->transmitter = transmitter;
link->link_version = version;
link->interface = interface;
link->drop_rate = drop_rate;
// TODO other link attributes...
}
}
send_please_explain(&context, my_subscriber, sender);
if (changed){
route_version++;
neighbour->path_version ++;
if (link_send_alarm.alarm>now || link_send_alarm.alarm==0){
unschedule(&link_send_alarm);
link_send_alarm.alarm=now;
// read all incoming packets first
link_send_alarm.deadline=now+10;
schedule(&link_send_alarm);
}
}
return 0;
}
// if a neighbour asks for a subscriber explaination, make sure we repeat relevant link information immediately.
void link_explained(struct subscriber *subscriber)
{
time_ms_t now = gettime_ms();
struct link_state *state = get_link_state(subscriber);
state->next_update = now;
update_alarm(now);
}
void link_interface_down(struct overlay_interface *interface)
{
clean_neighbours(gettime_ms());
}
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