QMAILREMOTE patch

A friend wants to DKIM-sign outgoing mail, probably using Kyle Wheeler's 
DKIM wrapper around qmail-remote 
(http://www.memoryhole.net/qmail/#dkim). But he doesn't want to confuse 
his package manager by moving aside the real qmail-remote binary and 
putting something else in its place.

Inspired by the QMAILQUEUE patch, we patched qmail-rspawn to look for 
QMAILREMOTE in its environment. The 0th arg to execvp() is either the 
value of the env var (if set), or "qmail-remote" as usual. We tested 
with various arguments to qmail-start.

When QMAILREMOTE is not set:

     May 21 08:13:29 magnetic-babysitter-netbsd7 nbqmailsend: delivery 
1: success: 
166.84.7.144_accepted_message./Remote_host_said:_250_ok_1495368789_qp_3818/


When QMAILREMOTE is set to an empty string, or a non-empty path (full or 
unqualified) of a program that does not exist:

     May 21 08:16:34 magnetic-babysitter-netbsd7 nbqmailsend: delivery 
1: failure: Unable_to_run_qmail-remote./


When QMAILREMOTE is set to /var/tmp/schmonz (a shell script that runs 
'exec qmail-remote "$@"'):

     May 21 08:22:19 magnetic-babysitter-netbsd7 nbqmailsend: delivery 
1: success: 
166.84.7.144_accepted_message./Remote_host_said:_250_ok_1495369319_qp_19267/


Does this patch look reasonable?


--- Makefile.orig	2007-11-30 20:22:54.000000000 +0000
+++ Makefile
@@ -1462,19 +1462,19 @@ tcpto.h readwrite.h timeoutconn.h timeou

  qmail-rspawn: \
  load qmail-rspawn.o spawn.o tcpto_clean.o now.o coe.o sig.a open.a \
-seek.a lock.a wait.a fd.a stralloc.a alloc.a substdio.a error.a str.a \
+seek.a lock.a wait.a fd.a stralloc.a alloc.a substdio.a error.a env.a 
str.a \
  auto_qmail.o auto_uids.o auto_spawn.o
  	./load qmail-rspawn spawn.o tcpto_clean.o now.o coe.o \
  	sig.a open.a seek.a lock.a wait.a fd.a stralloc.a alloc.a \
-	substdio.a error.a str.a auto_qmail.o auto_uids.o \
-	auto_spawn.o
+	substdio.a error.a env.a str.a auto_qmail.o auto_uids.o \
+	auto_spawn.o

  qmail-rspawn.0: \
  qmail-rspawn.8
  	nroff -man qmail-rspawn.8 > qmail-rspawn.0

  qmail-rspawn.o: \
-compile qmail-rspawn.c fd.h wait.h substdio.h exit.h fork.h error.h \
+compile qmail-rspawn.c fd.h wait.h substdio.h exit.h fork.h error.h 
env.h \
  tcpto.h
  	./compile qmail-rspawn.c

--- qmail-rspawn.c.orig	1998-06-15 10:53:16.000000000 +0000
+++ qmail-rspawn.c
@@ -5,6 +5,17 @@
  #include "fork.h"
  #include "error.h"
  #include "tcpto.h"
+#include "env.h"
+
+static char *qrargs[1] = { 0 };
+
+static void setup_qrargs()
+{
+ if (!qrargs[0])
+  qrargs[0] = env_get("QMAILREMOTE");
+ if(!qrargs[0])
+  qrargs[0] = "qmail-remote";
+}

  void initialize(argc,argv)
  int argc;
@@ -84,7 +95,9 @@ char *s; char *r; int at;
   int f;
   char *(args[5]);

- args[0] = "qmail-remote";
+ setup_qrargs();
+
+ args[0] = qrargs[0];
   args[1] = r + at + 1;
   args[2] = s;
   args[3] = r;