From 8dcc879ca0cb590e6840daf87231428ba36687b9 Mon Sep 17 00:00:00 2001
From: Hamish Coleman <hamish@zot.org>
Date: Sat, 1 Jul 2023 13:39:02 +0100
Subject: [PATCH] Simplify config and build process for libpcap tool

---
 Makefile                     |  1 -
 config.mak.in                |  1 -
 configure.ac                 | 15 +--------------
 scripts/hack_fakeautoconf.sh |  4 ----
 tools/Makefile               |  7 ++-----
 tools/n2n-decode.c           | 15 +++++++++++++++
 6 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/Makefile b/Makefile
index efa9fc4..fb64d4d 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,6 @@ export AR
 export CFLAGS
 export LDFLAGS
 export LDLIBS
-export TOOLS_ADDITIONAL
 
 -include config.mak
 
diff --git a/config.mak.in b/config.mak.in
index 92b833c..7db29d2 100644
--- a/config.mak.in
+++ b/config.mak.in
@@ -9,4 +9,3 @@ WINDRES=@WINDRES@
 CFLAGS=@CFLAGS@
 LDFLAGS=@LDFLAGS@
 LDLIBS_EXTRA=@LIBS@
-TOOLS_ADDITIONAL=@TOOLS_ADDITIONAL@
diff --git a/configure.ac b/configure.ac
index 8b1bae8..354eebe 100644
--- a/configure.ac
+++ b/configure.ac
@@ -66,19 +66,7 @@ AC_ARG_ENABLE([pcap],
     [AS_HELP_STRING([--enable-pcap], [support for pcap])],
     [], [enable_pcap=no])
 AS_IF([test "x$enable_pcap" != xno],
-    [AC_CHECK_LIB([pcap], [pcap_open_live],
-        [
-            AC_DEFINE([N2N_HAVE_PCAP], [1], [Have PCAP library])
-            LIBS="-lpcap ${LIBS}"
-            TOOLS_ADDITIONAL="$TOOLS_ADDITIONAL n2n-decode"
-
-            # TODO
-            # - pcap_set_immediate_mode has been available since libpcap 1.5
-            #   in 2013 - probably should remove this check
-            AC_CHECK_LIB([pcap], [pcap_set_immediate_mode],
-                AC_DEFINE([HAVE_PCAP_IMMEDIATE_MODE], [1], [Have pcap_immediate_mode])
-            )
-        ],
+    [AC_CHECK_LIB([pcap], [pcap_set_immediate_mode],,
         [AC_MSG_ERROR([pcap library not found])]
     )],
 )
@@ -104,7 +92,6 @@ AS_IF([test "x$enable_pthread" != xno],
 
 AC_SUBST(host)
 AC_SUBST(WINDRES)
-AC_SUBST(TOOLS_ADDITIONAL)
 AC_CONFIG_HEADERS(include/config.h)
 AC_CONFIG_FILES(config.mak)
 
diff --git a/scripts/hack_fakeautoconf.sh b/scripts/hack_fakeautoconf.sh
index 3744a22..414c0c9 100755
--- a/scripts/hack_fakeautoconf.sh
+++ b/scripts/hack_fakeautoconf.sh
@@ -26,10 +26,6 @@ LDFLAGS=$LDFLAGS
 LDLIBS_EXTRA=$LDLIBS
 EOF
 
-cat >tools/config.mak <<EOF
-TOOLS_ADDITIONAL=
-EOF
-
 cat <<EOF >include/config.h
 #define PACKAGE_VERSION "FIXME"
 #define PACKAGE_BUILDDATE "$(date)"
diff --git a/tools/Makefile b/tools/Makefile
index 8a49cdd..1de221c 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -15,8 +15,7 @@ LDFLAGS+=-L..
 
 N2N_LIB=../libn2n.a
 
-TOOLS=n2n-benchmark n2n-keygen n2n-route n2n-portfwd
-TOOLS+=$(TOOLS_ADDITIONAL)
+TOOLS=n2n-benchmark n2n-keygen n2n-route n2n-portfwd n2n-decode
 
 TESTS=tests-compress tests-elliptic tests-hashing tests-transform
 TESTS+=tests-wire
@@ -29,9 +28,7 @@ n2n-benchmark.o: $(N2N_LIB) $(HEADERS) ../config.mak
 n2n-keygen.o: $(N2N_LIB) $(HEADERS) ../config.mak
 n2n-route.o: $(N2N_LIB) $(HEADERS) ../config.mak
 n2n-portfwd.o: $(N2N_LIB) $(HEADERS) ../config.mak
-
-n2n-decode: n2n-decode.c $(N2N_LIB) $(HEADERS) ../config.mak
-	$(CC) $(CFLAGS) $< $(LDFLAGS) $(LDLIBS) -lpcap -o $@
+n2n-decode.o: $(N2N_LIB) $(HEADERS) ../config.mak
 
 # See comments in the topdir Makefile about how to generate coverage
 # data.
diff --git a/tools/n2n-decode.c b/tools/n2n-decode.c
index c11211c..a8c17dc 100644
--- a/tools/n2n-decode.c
+++ b/tools/n2n-decode.c
@@ -16,6 +16,10 @@
  *
  */
 
+#include "config.h"
+
+#ifdef HAVE_LIBPCAP
+
 #include <errno.h>             // for errno
 #include <pcap.h>
 #include <signal.h>            // for signal, SIGINT, SIGTERM
@@ -372,3 +376,14 @@ int main(int argc, char* argv[]) {
 
   return(rv);
 }
+
+#else
+
+#include <stdio.h>
+
+int main() {
+    printf("n2n was compiled without libpcap support");
+    return -1;
+}
+
+#endif /* HAVE_LIBPCAP */