From fe4e1fe75cab68428833b7402f863d0e2286427f Mon Sep 17 00:00:00 2001
From: Arseny Maslennikov <arseny@altlinux.org>
Date: Mon, 11 Dec 2017 20:30:09 +0300
Subject: [PATCH] dhcp.c: Provide a DHCP vendor class identifier in requests

---
 dhcp.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/dhcp.c b/dhcp.c
index be6805f..86e3a74 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -25,6 +25,7 @@
  */
 
 
+#include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
@@ -38,6 +39,7 @@
 #include <net/ethernet.h>
 #include <netinet/ip.h>
 #include <netinet/udp.h>
+#include <sys/utsname.h>
 #include <sys/time.h>
 #include <time.h>
 #include <fcntl.h>
@@ -49,6 +51,7 @@
 #include "frontend.h"
 
 #include "dhcp.h"
+#include "version.h"
 
 
 typedef int bp_int32;
@@ -68,6 +71,9 @@ typedef short bp_int16;
 #define DHCP_OPTION_SERVER		54
 #define DHCP_OPTION_OPTIONREQ	55
 #define DHCP_OPTION_MAXSIZE		57
+#define DHCP_OPTION_VENDORCLASS	60
+
+#define DHCP_VENDOR_CLASS_ID_PREFIX "ALT-Propagator"
 
 #define BOOTP_CLIENT_PORT	68
 #define BOOTP_SERVER_PORT	67
@@ -101,6 +107,34 @@ struct bootp_request {
 
 static const char vendor_cookie[] = { 99, 130, 83, 99, 255 };
 
+// This function's return value needs to be freed after use.
+static char* get_vendor_class_id() {
+	// mimicking dhcpcd
+	char* ret;
+	struct utsname u;
+	unsigned int sz = sizeof(DHCP_VENDOR_CLASS_ID_PREFIX) +
+		sizeof(VERSION);
+	if (uname(&u) != 0) {
+		if ((ret = malloc(sz)) == NULL) {
+			log_perror("malloc");
+			return ret;
+		}
+		sprintf(ret, "%s-%s", DHCP_VENDOR_CLASS_ID_PREFIX, VERSION);
+	}
+	else {
+		sz += sizeof(DHCP_VENDOR_CLASS_ID_PREFIX) +
+			strlen(u.sysname) + 1 +
+			strlen(u.release) + 1 +
+			strlen(u.machine) + 1;
+		if ((ret = malloc(sz)) == NULL) {
+			log_perror("malloc");
+			return ret;
+		}
+		sprintf(ret, "%s-%s:%s-%s:%s", DHCP_VENDOR_CLASS_ID_PREFIX, VERSION,
+				u.sysname, u.release, u.machine);
+	}
+    return ret;
+}
 
 static unsigned int verify_checksum(void * buf2, int length2)
 {
@@ -523,6 +557,7 @@ enum return_type perform_dhcp(struct interface_info * intf)
 	struct sockaddr_in broadcast_addr;
 	struct bootp_request breq, bresp;
 	unsigned char messageType;
+	char* vendorClass;
 	unsigned int lease;
 	short aShort;
 	int num_options;
@@ -565,6 +600,11 @@ enum return_type perform_dhcp(struct interface_info * intf)
 	broadcast_addr.sin_port = htons(BOOTP_SERVER_PORT);	/* bootp server */
 	memset(&broadcast_addr.sin_addr, 0xff, sizeof(broadcast_addr.sin_addr));  /* broadcast */
 
+	vendorClass = get_vendor_class_id();
+	add_vendor_code(&breq, DHCP_OPTION_VENDORCLASS,
+		strlen(vendorClass),
+		vendorClass);
+
 	log_message("DHCP: sending DISCOVER");
 
 	wait_message("Sending DHCP request...");
@@ -574,6 +614,7 @@ enum return_type perform_dhcp(struct interface_info * intf)
 	if (i != 0) {
 		stg1_info_message("No DHCP reply received.");
 		close(s);
+		free(vendorClass);
 		return RETURN_ERROR;
 	}
 
@@ -582,12 +623,16 @@ enum return_type perform_dhcp(struct interface_info * intf)
 	if (get_vendor_code(&bresp, DHCP_OPTION_SERVER, &server_addr.sin_addr)) {
 		close(s);
 		log_message("DHCPOFFER didn't include server address");
+		free(vendorClass);
 		return RETURN_ERROR;
 	}
 
 	init_vendor_codes(&breq);
 	messageType = DHCP_TYPE_REQUEST;
 	add_vendor_code(&breq, DHCP_OPTION_TYPE, 1, &messageType);
+	add_vendor_code(&breq, DHCP_OPTION_VENDORCLASS,
+		strlen(vendorClass),
+		vendorClass);
 	add_vendor_code(&breq, DHCP_OPTION_SERVER, 4, &server_addr.sin_addr);
 	add_vendor_code(&breq, DHCP_OPTION_REQADDR, 4, &bresp.yiaddr);
 
@@ -613,16 +658,19 @@ enum return_type perform_dhcp(struct interface_info * intf)
 
 	if (i != 0) {
 		close(s);
+		free(vendorClass);
 		return RETURN_ERROR;
 	}
 
 	if (get_vendor_code(&bresp, DHCP_OPTION_LEASE, &lease)) {
 		log_message("failed to get lease time\n");
+		free(vendorClass);
 		return RETURN_ERROR;
 	}
 	lease = ntohl(lease);
 
 	close(s);
+	free(vendorClass);
 
 	intf->netmask.s_addr = 0;
 	intf->broadcast.s_addr = 0;
-- 
2.10.4