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gossipd: extract common functionality. 

This will be needed by Dijkstra as well.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2019-04-17 17:05:01 +09:30
parent 6dfa46d65a
commit 594af8049b
1 changed files with 72 additions and 38 deletions
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110
gossipd/routing.c
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@ -474,6 +474,70 @@ static bool fuzz_fee(u64 *fee, double fee_scale)
return true;
}
/* Can we carry this amount across the channel? If so, returns true and
* sets newtotal and newrisk */
static bool can_reach(const struct half_chan *c,
struct amount_msat total,
struct amount_msat risk,
double riskfactor, double fee_scale,
struct amount_msat *newtotal, struct amount_msat *newrisk)
{
/* FIXME: Bias against smaller channels. */
struct amount_msat fee;
if (!amount_msat_fee(&fee, total, c->base_fee, c->proportional_fee))
return false;
if (!fuzz_fee(&fee.millisatoshis, fee_scale)) /* Raw: double manipulation */
return false;
if (!amount_msat_add(newtotal, total, fee))
return false;
/* Skip a channel if it indicated that it won't route the
* requested amount. */
if (!hc_can_carry(c, *newtotal))
return false;
*newrisk = risk;
if (!risk_add_fee(newrisk, *newtotal, c->delay, riskfactor))
return false;
return true;
}
/* Does totala+riska add up to less than totalb+riskb?
* Saves sums if you want them.
*/
static bool costs_less(struct amount_msat totala,
struct amount_msat riska,
struct amount_msat *costa,
struct amount_msat totalb,
struct amount_msat riskb,
struct amount_msat *costb)
{
struct amount_msat suma, sumb;
if (!amount_msat_add(&suma, totala, riska))
return false;
if (!amount_msat_add(&sumb, totalb, riskb)) {
/* We calculated this before: shouldn't happen! */
status_broken("Overflow: total %s + risk %s",
type_to_string(tmpctx, struct amount_msat,
&totalb),
type_to_string(tmpctx, struct amount_msat,
&riskb));
return false;
}
if (costa)
*costa = suma;
if (costb)
*costb = sumb;
return amount_msat_less(suma, sumb);
}
/* We track totals, rather than costs. That's because the fee depends
* on the current amount passing through. */
static void bfg_one_edge(struct node *node,
@ -499,49 +563,19 @@ static void bfg_one_edge(struct node *node,
for (h = 0; h < max_hops; h++) {
struct node *src;
/* FIXME: Bias against smaller channels. */
struct amount_msat fee, risk, requiredcap,
this_total, curr_total;
struct amount_msat total, risk;
if (!amount_msat_fee(&fee, node->bfg[h].total,
c->base_fee, c->proportional_fee))
continue;
if (!fuzz_fee(&fee.millisatoshis, fee_scale)) /* Raw: double manipulation */
continue;
if (!amount_msat_add(&requiredcap, node->bfg[h].total, fee))
continue;
risk = node->bfg[h].risk;
if (!risk_add_fee(&risk, requiredcap, c->delay, riskfactor))
continue;
if (!hc_can_carry(c, requiredcap)) {
/* Skip a channel if it indicated that it won't route
* the requested amount. */
continue;
}
if (!amount_msat_add(&this_total, requiredcap, risk))
if (!can_reach(c, node->bfg[h].total, node->bfg[h].risk,
riskfactor, fee_scale, &total, &risk))
continue;
/* nodes[0] is src for connections[0] */
src = chan->nodes[idx];
if (!amount_msat_add(&curr_total,
src->bfg[h + 1].total,
src->bfg[h + 1].risk)) {
/* We just calculated this: shouldn't happen! */
status_broken("Overflow: total %s + risk %s",
type_to_string(tmpctx, struct amount_msat,
&src->bfg[h + 1].total),
type_to_string(tmpctx, struct amount_msat,
&src->bfg[h + 1].risk));
continue;
}
if (amount_msat_less(this_total, curr_total)) {
if (costs_less(total, risk, NULL,
src->bfg[h + 1].total,
src->bfg[h + 1].risk,
NULL)) {
SUPERVERBOSE("...%s can reach here hoplen %zu"
" total %s risk %s",
type_to_string(tmpctx, struct node_id,
@ -551,7 +585,7 @@ static void bfg_one_edge(struct node *node,
&requiredcap),
type_to_string(tmpctx, struct amount_msat,
&risk));
src->bfg[h+1].total = requiredcap;
src->bfg[h+1].total = total;
src->bfg[h+1].risk = risk;
src->bfg[h+1].prev = chan;
}