RFC: Handle Symbolic links in the Gateway

core/coreapi/interface/errors.go

@@ -3,6 +3,7 @@ package iface
 import "errors"
 
 var (
-	ErrIsDir   = errors.New("object is a directory")
-	ErrOffline = errors.New("can't resolve, ipfs node is offline")
+	ErrIsDir     = errors.New("object is a directory")
+	ErrOffline   = errors.New("can't resolve, ipfs node is offline")
+	ErrIsSymLink = errors.New("object is a symbolic link")
 )

core/coreapi/interface/unixfs.go

@@ -17,4 +17,7 @@ type UnixfsAPI interface {
 
 	// Ls returns the list of links in a directory
 	Ls(context.Context, Path) ([]*ipld.Link, error)
+
+	// ReadSymLink returns the contents of a symbolic link
+	ReadSymLink(context.Context, Path) (string, error)
 }

core/coreapi/unixfs.go

@@ -2,12 +2,16 @@ package coreapi
 
 import (
 	"context"
+	"errors"
 	"io"
 
 	coreiface "github.com/ipfs/go-ipfs/core/coreapi/interface"
 	coreunix "github.com/ipfs/go-ipfs/core/coreunix"
+	mdag "github.com/ipfs/go-ipfs/merkledag"
 	uio "github.com/ipfs/go-ipfs/unixfs/io"
+	ftpb "github.com/ipfs/go-ipfs/unixfs/pb"
 
+	proto "gx/ipfs/QmZ4Qi3GaRbjcx28Sme5eMH7RQjGkt8wHxt2a65oLaeFEV/gogo-protobuf/proto"
 	cid "gx/ipfs/QmcZfnkapfECQGcLZaf9B79NRg7cRa9EnZh4LSbkCzwNvY/go-cid"
 	ipld "gx/ipfs/Qme5bWv7wtjUNGsK2BNGVUFPKiuxWrsqrtvYwCLRw8YFES/go-ipld-format"
 )
@@ -38,12 +42,14 @@ func (api *UnixfsAPI) Cat(ctx context.Context, p coreiface.Path) (coreiface.Read
 	}
 
 	r, err := uio.NewDagReader(ctx, dagnode, dget)
-	if err == uio.ErrIsDir {
+	switch err {
+	case uio.ErrIsDir:
 		return nil, coreiface.ErrIsDir
-	} else if err != nil {
-		return nil, err
+	case uio.ErrCantReadSymlinks:
+		return nil, coreiface.ErrIsSymLink
+	default:
 	}
-	return r, nil
+	return r, err
 }
 
 // Ls returns the contents of an IPFS or IPNS object(s) at path p, with the format:
@@ -76,6 +82,30 @@ func (api *UnixfsAPI) Ls(ctx context.Context, p coreiface.Path) ([]*ipld.Link, e
 	return links, nil
 }
 
+var NotASymLink = errors.New("not a symbolic link")
+
+func (api *UnixfsAPI) ReadSymLink(ctx context.Context, p coreiface.Path) (string, error) {
+	dagnode, err := api.core().ResolveNode(ctx, p)
+	if err != nil {
+		return "", err
+	}
+	switch n := dagnode.(type) {
+	case *mdag.ProtoNode:
+		pb := new(ftpb.Data)
+		if err := proto.Unmarshal(n.Data(), pb); err != nil {
+			return "", err
+		}
+		switch pb.GetType() {
+		case ftpb.Data_Symlink:
+			return string(pb.GetData()), nil
+		default:
+			return "", NotASymLink
+		}
+	default:
+		return "", NotASymLink
+	}
+}
+
 func (api *UnixfsAPI) core() coreiface.CoreAPI {
 	return (*CoreAPI)(api)
 }

core/corehttp/gateway_handler.go

@@ -185,12 +185,15 @@ func (i *gatewayHandler) getOrHeadHandler(ctx context.Context, w http.ResponseWr
 
 	dr, err := i.api.Unixfs().Cat(ctx, resolvedPath)
 	dir := false
+	symLink := false
 	switch err {
 	case nil:
 		// Cat() worked
 		defer dr.Close()
 	case coreiface.ErrIsDir:
 		dir = true
+	case coreiface.ErrIsSymLink:
+		symLink = true
 	default:
 		webError(w, "ipfs cat "+escapedURLPath, err, http.StatusNotFound)
 		return
@@ -266,6 +269,18 @@ func (i *gatewayHandler) getOrHeadHandler(ctx context.Context, w http.ResponseWr
 		modtime = time.Unix(1, 0)
 	}
 
+	if symLink {
+		link, err := i.api.Unixfs().ReadSymLink(ctx, resolvedPath)
+		if err != nil {
+			internalWebError(w, err)
+			return
+		}
+		newPath := gopath.Join(gopath.Dir(urlPath), link)
+		http.Redirect(w, r, newPath, 302)
+		log.Debugf("symlink: redirect to %s", newPath)
+		return
+	}
+
 	if !dir {
 		name := gopath.Base(urlPath)
 		i.serveFile(w, r, name, modtime, dr)

test/sharness/t0110-gateway.sh

@@ -193,6 +193,46 @@ test_expect_success "GET compact blocks succeeds" '
   test_cmp expected actual
 '
 
+#
+#
+#
+
+test_expect_success "create dir with symbolic links" '
+  mkdir dirwlinks/ &&
+  ( cd dirwlinks &&
+    echo "A Simple File" > afile &&
+    ln -s afile linktofile &&
+    mkdir adir &&
+    echo "Another File" > adir/bfile &&
+    ln -s adir linktodir
+  )
+'
+
+test_expect_success "add dir with symbolic links" '
+  DIRHASH=$(ipfs add -Q -r dirwlinks)
+  echo $DIRHASH
+'
+
+test_expect_success "getting afile works" '
+  curl -L -o actual "http://127.0.0.1:$port/ipfs/$DIRHASH/afile" &&
+  test_cmp dirwlinks/afile actual
+'
+
+test_expect_success "getting linktofile works" '
+  curl -L -o actual "http://127.0.0.1:$port/ipfs/$DIRHASH/linktofile" &&
+  test_cmp dirwlinks/afile actual
+'
+
+test_expect_success "getting adir/bfile works" '
+  curl -L -o actual "http://127.0.0.1:$port/ipfs/$DIRHASH/adir/bfile" &&
+  test_cmp dirwlinks/adir/bfile actual
+'
+
+test_expect_failure "getting linktodir/bfile works" '
+  curl -L -o actual "http://127.0.0.1:$port/ipfs/$DIRHASH/linktodir/bfile" &&
+  test_cmp dirwlinks/adir/bfile actual
+'
+
 test_kill_ipfs_daemon
 
 test_done