add config options for proxy/subdomain

Co-authored-by: Steven <steven@stebalien.com>

gateway.go

@@ -1,11 +1,71 @@
 package config
 
+type GatewaySpec struct {
+	// Paths is explicit list of path prefixes that should be handled by
+	// this gateway. Example: `["/ipfs", "/ipns", "/api"]`
+	Paths []string
+
+	// UseSubdomains indicates whether or not this gateway uses subdomains
+	// for IPFS resources instead of paths. That is: http://CID.ipfs.GATEWAY/...
+	//
+	// If this flag is set, any /ipns/$id and/or /ipfs/$id paths in PathPrefixes
+	// will be permanently redirected to http://$id.[ipns|ipfs].$gateway/.
+	//
+	// We do not support using both paths and subdomains for a single domain
+	// for security reasons (Origin isolation).
+	UseSubdomains bool
+
+	// NoDNSLink configures this gateway to _not_ resolve DNSLink for the FQDN
+	// provided in `Host` HTTP header.
+	NoDNSLink bool
+}
+
 // Gateway contains options for the HTTP gateway server.
 type Gateway struct {
-	HTTPHeaders  map[string][]string // HTTP headers to return with the gateway
+
+	// HTTPHeaders configures the headers that should be returned by this
+	// gateway.
+	HTTPHeaders map[string][]string // HTTP headers to return with the gateway
+
+	// RootRedirect is the path to which requests to `/` on this gateway
+	// should be redirected.
 	RootRedirect string
-	Writable     bool
+
+	// Writable enables PUT/POST request handling by this gateway. Usually,
+	// writing is done through the API, not the gateway.
+	Writable bool
+
+	// PathPrefixes  is an array of acceptable url paths that a client can
+	// specify in X-Ipfs-Path-Prefix header.
+	//
+	// The X-Ipfs-Path-Prefix header is used to specify a base path to prepend
+	// to links in directory listings and for trailing-slash redirects. It is
+	// intended to be set by a frontend http proxy like nginx.
+	//
+	// Example: To mount blog.ipfs.io (a DNSLink site) at ipfs.io/blog
+	// set PathPrefixes to ["/blog"] and nginx config to translate paths
+	// and pass Host header (for DNSLink):
+	//  location /blog/ {
+	//    rewrite "^/blog(/.*)$" $1 break;
+	//    proxy_set_header Host blog.ipfs.io;
+	//    proxy_set_header X-Ipfs-Gateway-Prefix /blog;
+	//    proxy_pass http://127.0.0.1:8080;
+	//  }
 	PathPrefixes []string
-	APICommands  []string
-	NoFetch      bool
+
+	// FIXME: Not yet implemented
+	APICommands []string
+
+	// NoFetch configures the gateway to _not_ fetch blocks in response to
+	// requests.
+	NoFetch bool
+
+	// NoDNSLink configures the gateway to _not_ perform DNS TXT record
+	// lookups in response to requests with values in `Host` HTTP header.
+	// This flag can be overriden per FQDN in PublicGateways.
+	NoDNSLink bool
+
+	// PublicGateways configures behavior of known public gateways.
+	// Each key is a fully qualified domain name (FQDN).
+	PublicGateways map[string]*GatewaySpec
 }