ldpd: simplify initialization of the child processes

In order to have separate ASLR/cookies per process, ldpd calls exec()
in the child processes after fork() (this is also known as the fork+exec
model).

This is an important security feature but it makes the initialization
of the child processes a bit more complicated as they're not a copy of
the parent anymore, so all parameters given via command line are lost.

To solve this problem, we were creating an argv array by hand with all
necessary parameters and providing it to the exec() syscall. This works
but it's a very ugly solution. This patch introduces a different approach
to solve the problem: send an IMSG_INIT message to the child processes
with all parameters they need in order to initialize properly. This
makes adding additional initialization parameters much more convenient
and less error prone.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

1 files changed, 11 insertions, 2 deletions

diff --git a/ldpd/ldpd.h b/ldpd/ldpd.h
index ad83b9aad..cba1939d9 100644
--- a/ldpd/ldpd.h
+++ b/ldpd/ldpd.h
@@ -145,7 +145,16 @@ enum imsg_type {
 	IMSG_RECONF_END,
 	IMSG_DEBUG_UPDATE,
 	IMSG_LOG,
-	IMSG_ACL_CHECK
+	IMSG_ACL_CHECK,
+	IMSG_INIT
+};
+
+struct ldpd_init {
+	char		 user[256];
+	char		 group[256];
+	char		 ctl_sock_path[MAXPATHLEN];
+	char		 zclient_serv_path[MAXPATHLEN];
+	u_short		 instance;
 };
 
 union ldpd_addr {
@@ -508,7 +517,6 @@ struct ldpd_af_global {
 struct ldpd_global {
 	int			 cmd_opts;
 	int			 sighup;
-	time_t			 uptime;
 	struct in_addr		 rtr_id;
 	struct ldpd_af_global	 ipv4;
 	struct ldpd_af_global	 ipv6;
@@ -652,6 +660,7 @@ struct ctl_pw {
 
 extern struct ldpd_conf		*ldpd_conf, *vty_conf;
 extern struct ldpd_global	 global;
+extern struct ldpd_init		 init;
 
 /* parse.y */
 struct ldpd_conf	*parse_config(char *);