From 848d4c7f18649b4c994af01dd6fb6b4764cb1127 Mon Sep 17 00:00:00 2001
From: Marcin Rataj <lidel@lidel.org>
Date: Sat, 7 Mar 2020 01:56:48 +0100
Subject: [PATCH] feat: IPFS_NS_MAP

Allows static DNSLink mappings with IPFS_NS_MAP.

License: MIT
Signed-off-by: Marcin Rataj <lidel@lidel.org>
---
 docs/environment-variables.md | 14 ++++++++++++++
 namesys/cache.go              |  8 ++++++++
 namesys/namesys.go            | 25 +++++++++++++++++++++++--
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/docs/environment-variables.md b/docs/environment-variables.md
index 82eb5c3126c..fdc92f461c3 100644
--- a/docs/environment-variables.md
+++ b/docs/environment-variables.md
@@ -82,6 +82,20 @@ the `--migrate` flag).
 
 Default: https://ipfs.io/ipfs/$something (depends on the IPFS version)
 
+## `IPFS_NS_MAP`
+
+Prewarms namesys cache with static records for deteministic tests and debugging.
+Useful for testing things like DNSLink without real DNS lookup.
+
+Example:
+
+```console
+$ IPFS_NS_MAP="dnslink-test1.example.com:/ipfs/bafkreicysg23kiwv34eg2d7qweipxwosdo2py4ldv42nbauguluen5v6am,dnslink-test2.example.com:/ipns/dnslink-test1.example.com" ipfs daemon
+...
+$ ipfs resolve -r /ipns/dnslink-test2.example.com
+/ipfs/bafkreicysg23kiwv34eg2d7qweipxwosdo2py4ldv42nbauguluen5v6am
+```
+
 ## `LIBP2P_MUX_PREFS`
 
 Tells go-ipfs which multiplexers to use in which order.
diff --git a/namesys/cache.go b/namesys/cache.go
index 4a5cb5113ae..a0029829d33 100644
--- a/namesys/cache.go
+++ b/namesys/cache.go
@@ -7,6 +7,14 @@ import (
 )
 
 func (ns *mpns) cacheGet(name string) (path.Path, bool) {
+	// existence of optional mapping defined via IPFS_NS_MAP is checked first
+	if ns.staticMap != nil {
+		val, ok := ns.staticMap[name]
+		if ok {
+			return val, true
+		}
+	}
+
 	if ns.cache == nil {
 		return "", false
 	}
diff --git a/namesys/namesys.go b/namesys/namesys.go
index 079eecccc03..11f4646f174 100644
--- a/namesys/namesys.go
+++ b/namesys/namesys.go
@@ -2,6 +2,7 @@ package namesys
 
 import (
 	"context"
+	"os"
 	"strings"
 	"time"
 
@@ -29,25 +30,45 @@ type mpns struct {
 	dnsResolver, proquintResolver, ipnsResolver resolver
 	ipnsPublisher                               Publisher
 
-	cache *lru.Cache
+	staticMap map[string]path.Path
+	cache     *lru.Cache
 }
 
 // NewNameSystem will construct the IPFS naming system based on Routing
 func NewNameSystem(r routing.ValueStore, ds ds.Datastore, cachesize int) NameSystem {
-	var cache *lru.Cache
+	var (
+		cache     *lru.Cache
+		staticMap map[string]path.Path
+	)
 	if cachesize > 0 {
 		cache, _ = lru.New(cachesize)
 	}
 
+	// Prewarm namesys cache with static records for deteministic tests and debugging.
+	// Useful for testing things like DNSLink without real DNS lookup.
+	// Example:
+	// IPFS_NS_MAP="dnslink-test.example.com:/ipfs/bafkreicysg23kiwv34eg2d7qweipxwosdo2py4ldv42nbauguluen5v6am"
+	if list := os.Getenv("IPFS_NS_MAP"); list != "" {
+		staticMap = make(map[string]path.Path)
+		for _, pair := range strings.Split(list, ",") {
+			mapping := strings.SplitN(pair, ":", 2)
+			key := mapping[0]
+			value := path.FromString(mapping[1])
+			staticMap[key] = value
+		}
+	}
+
 	return &mpns{
 		dnsResolver:      NewDNSResolver(),
 		proquintResolver: new(ProquintResolver),
 		ipnsResolver:     NewIpnsResolver(r),
 		ipnsPublisher:    NewIpnsPublisher(r, ds),
+		staticMap:        staticMap,
 		cache:            cache,
 	}
 }
 
+// DefaultResolverCacheTTL defines max ttl of a record placed in namesys cache.
 const DefaultResolverCacheTTL = time.Minute
 
 // Resolve implements Resolver.