From cfffd129e3c44353ac645dc4fb2bd227fceeeac3 Mon Sep 17 00:00:00 2001
From: Nick Owens <mischief@offblast.org>
Date: Fri, 5 Feb 2016 14:29:16 -0800
Subject: [PATCH] p/srv: properly fallback to uname with ~0 uid in dotu

---
 p/srv/fcall.go | 41 +++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/p/srv/fcall.go b/p/srv/fcall.go
index 55779bb..21892dd 100644
--- a/p/srv/fcall.go
+++ b/p/srv/fcall.go
@@ -45,6 +45,31 @@ func (srv *Srv) version(req *Req) {
 	req.RespondRversion(conn.Msize, ver)
 }
 
+func (srv *Srv) getUser(req *Req) p.User {
+	tc := req.Tc
+	conn := req.Conn
+
+	var user p.User = nil
+
+	if conn.Dotu {
+		// from the 9p2000.u specification:
+		// A numeric uname field has been added to the attach and auth
+		// messages in order to provide hints to map a string to a
+		// numeric id if such a facility is not available. The numeric
+		// uname should be given preference over the uname string
+		// unless n_uname is unspecified (~0).
+		if tc.Unamenum != p.NOUID {
+			user = srv.Upool.Uid2User(int(tc.Unamenum))
+		} else if tc.Uname != "" {
+			user = srv.Upool.Uname2User(tc.Uname)
+		}
+	} else if tc.Uname != "" {
+		user = srv.Upool.Uname2User(tc.Uname)
+	}
+
+	return user
+}
+
 func (srv *Srv) auth(req *Req) {
 	tc := req.Tc
 	conn := req.Conn
@@ -59,13 +84,7 @@ func (srv *Srv) auth(req *Req) {
 		return
 	}
 
-	var user p.User = nil
-	if tc.Unamenum != p.NOUID || conn.Dotu {
-		user = srv.Upool.Uid2User(int(tc.Unamenum))
-	} else if tc.Uname != "" {
-		user = srv.Upool.Uname2User(tc.Uname)
-	}
-
+	user := srv.getUser(req)
 	if user == nil {
 		req.RespondError(Enouser)
 		return
@@ -114,13 +133,7 @@ func (srv *Srv) attach(req *Req) {
 		}
 	}
 
-	var user p.User = nil
-	if tc.Unamenum != p.NOUID || conn.Dotu {
-		user = srv.Upool.Uid2User(int(tc.Unamenum))
-	} else if tc.Uname != "" {
-		user = srv.Upool.Uname2User(tc.Uname)
-	}
-
+	user := srv.getUser(req)
 	if user == nil {
 		req.RespondError(Enouser)
 		return