From 1d487dc6a682468ae00402b3720ff412b6bfb6fc Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Mon, 5 Mar 2012 19:19:29 +0100
Subject: [PATCH] nix-worker: put the pid of the caller in argv[1]

This is useful for debugging.
---
 src/libmain/shared.cc        |  4 +++-
 src/libmain/shared.hh        |  2 ++
 src/nix-worker/nix-worker.cc | 21 ++++++++++++++++++++-
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index d3b73f8fd..99ac198ca 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -287,7 +287,7 @@ static void * oomHandler(size_t requested)
 
 
 int exitCode = 0;
-
+char * * argvSaved = 0;
 
 }
 
@@ -298,6 +298,8 @@ int main(int argc, char * * argv)
 {
     using namespace nix;
 
+    argvSaved = argv;
+
     /* If we're setuid, then we need to take some security precautions
        right away. */
     if (argc == 0) abort();
diff --git a/src/libmain/shared.hh b/src/libmain/shared.hh
index 1d6a6ec57..43725e07f 100644
--- a/src/libmain/shared.hh
+++ b/src/libmain/shared.hh
@@ -56,6 +56,8 @@ struct RemoveTempRoots
 /* Exit code of the program. */
 extern int exitCode;
 
+extern char * * argvSaved;
+
 }
 
 
diff --git a/src/nix-worker/nix-worker.cc b/src/nix-worker/nix-worker.cc
index eaa686667..7ca54dee9 100644
--- a/src/nix-worker/nix-worker.cc
+++ b/src/nix-worker/nix-worker.cc
@@ -753,8 +753,21 @@ static void daemonLoop()
 		    throw SysError("accepting connection");
             }
 
-            printMsg(lvlInfo, format("accepted connection %1%") % remote);
+            /* Get the identity of the caller, if possible. */
+            uid_t clientUid = -1;
+            pid_t clientPid = -1;
 
+#if defined(SO_PEERCRED)
+            ucred cred;
+            socklen_t credLen = sizeof(cred);
+            if (getsockopt(remote, SOL_SOCKET, SO_PEERCRED, &cred, &credLen) != -1) {
+                clientPid = cred.pid;
+                clientUid = cred.uid;
+            }
+#endif
+
+            printMsg(lvlInfo, format("accepted connection from pid %1%, uid %2%") % clientPid % clientUid);
+            
             /* Fork a child to handle the connection. */
             pid_t child;
             child = fork();
@@ -774,6 +787,12 @@ static void daemonLoop()
                     /* Restore normal handling of SIGCHLD. */
                     setSigChldAction(false);
 
+                    /* For debugging, stuff the pid into argv[1]. */
+                    if (clientPid != -1 && argvSaved[1]) {
+                        string processName = int2String(clientPid);
+                        strncpy(argvSaved[1], processName.c_str(), strlen(argvSaved[1]));
+                    }
+                    
                     /* Since the daemon can be long-running, the
                        settings may have changed.  So force a reload. */
                     reloadSettings();