From: Ralf Jung <post@ralfj.de>
Date: Fri, 9 Aug 2013 20:03:13 +0000 (+0200)
Subject: run nsupdate as child and send it the update commands
X-Git-Url: https://git.ralfj.de/dyn-nsupdate.git/commitdiff_plain/48ce26b2492550b08316b63c42ac1afe63c8c12b

run nsupdate as child and send it the update commands
---

diff --git a/dyn-nsupdate.cpp b/dyn-nsupdate.cpp
index cdd1dc4..4cb7ead 100644
--- a/dyn-nsupdate.cpp
+++ b/dyn-nsupdate.cpp
@@ -1,12 +1,25 @@
 #include <iostream>
 #include <fstream>
+#include <sys/wait.h>
 
 #include <boost/regex.hpp>
 #include <boost/property_tree/ptree.hpp>
 #include <boost/property_tree/ini_parser.hpp>
+#include <boost/iostreams/device/file_descriptor.hpp>
+#include <boost/iostreams/stream.hpp>
 
 using namespace boost;
 
+static void write(int fd, const char *str)
+{
+	size_t len = strlen(str);
+	ssize_t written = write(fd, str, len);
+	if (written < 0 || (size_t)written != len) {
+		std::cerr << "Error writing pipe." << std::endl;
+		exit(1);
+	}
+}
+
 int main(int argc, const char ** argv)
 {
 	static const regex regex_ip("\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3}");
@@ -26,31 +39,78 @@ int main(int argc, const char ** argv)
 	
 	if (!regex_match(ip, regex_ip)) {
 		std::cerr << "Invalid IP address " << ip << "." << std::endl;
-		return 1;
+		exit(1);
 	}
 	if (!regex_match(user, regex_user)) {
 		std::cerr << "Invalid username " << user << "." << std::endl;
-		return 1;
+		exit(1);
 	}
 	
 	/* read configuration */
 	property_tree::ptree config;
 	property_tree::ini_parser::read_ini(CONFIG_FILE, config);
+	std::string nsupdate = config.get<std::string>("nsupdate");
 	std::string keyfile = config.get<std::string>("key");
 	
 	/* Check username, password, domain */
 	optional<std::string> correct_password = config.get_optional<std::string>(user+".password");
 	if (!correct_password || *correct_password != password) {
 		std::cerr << "Username or password incorrect." << std::endl;
-		return 1;
+		exit(1);
 	}
 	if (config.get<std::string>(user+".domain") != domain) {
 		std::cerr << "Domain incorrect." << std::endl;
-		return 1;
+		exit(1);
 	}
 	
-	std::cout << "It's all right, using key " << keyfile << std::endl;
+	/* preapre the pipe */
+	int pipe_ends[] = {0,0};
+	pipe(pipe_ends);
+
+	/* Launch nsupdate */
+	pid_t child_pid = fork();
+	if (child_pid < 0) {
+		std::cerr << "Error while forking." << std::endl;
+		exit(1);
+	}
+	if (child_pid == 0) {
+		/* We're in the child */
+		/* Close write end, use read and as stdin */
+		close(pipe_ends[1]);
+		dup2(pipe_ends[0], fileno(stdin));
+		/* exec nsupdate */
+		execl(nsupdate.c_str(), nsupdate.c_str(), "-k", keyfile.c_str(), NULL);
+		/* There was an error */
+		std::cerr << "There was an error executing nsupdate." << std::endl;
+		exit(1);
+	}
+	
+	/* Send it the command */
+	write(pipe_ends[1], "server localhost\n");
+	
+	write(pipe_ends[1], "update delete ");
+	write(pipe_ends[1], domain.c_str());
+	write(pipe_ends[1], ".\n");
 	
+	write(pipe_ends[1], "update add ");
+	write(pipe_ends[1], domain.c_str());
+	write(pipe_ends[1], ". 60 A ");
+	write(pipe_ends[1], ip.c_str());
+	write(pipe_ends[1], "\n");
+	
+	write(pipe_ends[1], "send\n");
+	
+	/* Close both ends */
+	close(pipe_ends[0]);
+	close(pipe_ends[1]);
+	
+	/* Wait for child to be gone */
+	int child_status;
+	waitpid(child_pid, &child_status, 0);
+	if (child_status != 0) {
+		std::cerr << "There was an error in the child." << std::endl;
+		exit(1);
+	}
 	
 	return 0;
 }