PS,SD: Use new path lookup strategy

[lukedirtwalker]

Integrates the new path lookup strategy into sciond and PS.

This is a breaking change, the PS and sciond have completely different semantics for path lookups.

Fixes #2834
Fixes #2835
Fixes #2454

This change is 

[oncilla]

Reviewed 14 of 14 files at r1.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @lukedirtwalker)

---

go/path_srv/main.go, line 164 at r1 (raw file):

	deduper := handlers.NewGetSegsDeduper(msger)
	if core {
		segReqHandler = handlers.NewSegReqCoreHandler(args, deduper)

No dedupe 💯

---

go/sciond/internal/fetcher/fetcher.go, line 64 at r1 (raw file):

	revCache revcache.RevCache, cfg config.SDConfig, logger log.Logger) *Fetcher {

	localIA := itopo.Get().ISD_AS

do not call itopo directly.

---

go/sciond/internal/fetcher/fetcher.go, line 88 at r1 (raw file):

	handler := &fetcherHandler{
		Fetcher:  f,
		topology: itopo.Get(),

replace that too,

---

go/sciond/internal/fetcher/fetcher.go, line 283 at r1 (raw file):

		Intfs: intfs,
	}
	// this is a bit involved, we have to delete the next query cache,

why can we not just delete all NQ that either start or end with the current IA?

[lukedirtwalker]

Reviewable status: 12 of 17 files reviewed, 3 unresolved discussions (waiting on @oncilla)

---

go/path_srv/main.go, line 164 at r1 (raw file):

Previously, Oncilla wrote…

No dedupe 💯

🎉

---

go/sciond/internal/fetcher/fetcher.go, line 64 at r1 (raw file):

Previously, Oncilla wrote…

do not call itopo directly.

Done.

---

go/sciond/internal/fetcher/fetcher.go, line 88 at r1 (raw file):

Previously, Oncilla wrote…

replace that too,

Done.

---

go/sciond/internal/fetcher/fetcher.go, line 283 at r1 (raw file):

Previously, Oncilla wrote…

why can we not just delete all NQ that either start or end with the current IA?

I tried to do that (if you look into the history) but that isn't enough. For example a down segment can pass through your AS and will be deleted but the next query would still be in there. It actually took me quite some time to figure out what was wrong. The way it is now it should work in any case 🤞 . Tried to improve the comment.

Also hopefully we can remove this once we change the refresh flag (#2871)

[oncilla]

Reviewed 5 of 5 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved

[oncilla]

Reviewed 3 of 3 files at r3.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @lukedirtwalker)

---

go/lib/infra/messenger/addr.go, line 126 at r3 (raw file):

	newAddr := snetAddr.Copy()

	defer func() {

why as a defer and not simple statement?

[lukedirtwalker]

Reviewable status: 12 of 20 files reviewed, 1 unresolved discussion (waiting on @oncilla)

---

go/lib/infra/messenger/addr.go, line 126 at r3 (raw file):

Previously, Oncilla wrote…

why as a defer and not simple statement?

Because I want to have it printed on every exit path here. (note that newAddr.ǸextHop is set in the code below.)

[oncilla]

Reviewed 8 of 9 files at r4.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @oncilla)

[oncilla]

Reviewable status: complete! all files reviewed, all discussions resolved