From 7f6721bb8283d11644794f436cae3ec7bf16de3e Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Mon, 18 Jul 2011 10:47:35 -0400
Subject: [PATCH] Pass around the DHCP message type as the literal data, not as
 a character pointer to the matching data in the options field of the DHCP
 packet.

---
 ndhc/dhcp.c  | 14 ++++++++------
 ndhc/state.c | 20 ++++++++++----------
 ndhc/state.h |  2 +-
 3 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/ndhc/dhcp.c b/ndhc/dhcp.c
index 2200360..acb190b 100644
--- a/ndhc/dhcp.c
+++ b/ndhc/dhcp.c
@@ -480,9 +480,8 @@ void set_listen_none(struct client_state_t *cs)
 }
 
 static int validate_dhcp_packet(struct client_state_t *cs, int len,
-                                struct dhcpmsg *packet, uint8_t **msg)
+                                struct dhcpmsg *packet, uint8_t *msgtype)
 {
-    ssize_t optlen;
     if (len < sizeof *packet - sizeof packet->options) {
         log_line("Packet is too short to contain magic cookie.  Ignoring.");
         return 0;
@@ -496,16 +495,19 @@ static int validate_dhcp_packet(struct client_state_t *cs, int len,
                  packet->xid, cs->xid);
         return 0;
     }
-    if (!(*msg = get_option_data(packet, DHCP_MESSAGE_TYPE, &optlen))) {
+    ssize_t optlen;
+    uint8_t *temp = get_option_data(packet, DHCP_MESSAGE_TYPE, &optlen);
+    if (!temp) {
         log_line("Packet does not specify a DHCP message type.  Ignoring.");
         return 0;
     }
+    *msgtype = *temp;
     return 1;
 }
 
 void handle_packet(struct client_state_t *cs)
 {
-    uint8_t *message = NULL;
+    uint8_t msgtype;
     int len;
     struct dhcpmsg packet;
 
@@ -523,9 +525,9 @@ void handle_packet(struct client_state_t *cs)
         change_listen_mode(cs, cs->listenMode);
     }
 
-    if (!validate_dhcp_packet(cs, len, &packet, &message))
+    if (!validate_dhcp_packet(cs, len, &packet, &msgtype))
         return;
-    packet_action(cs, &packet, message);
+    packet_action(cs, &packet, msgtype);
 }
 
 static void add_option_vendor(struct dhcpmsg *packet)
diff --git a/ndhc/state.c b/ndhc/state.c
index 75e14da..098aad2 100644
--- a/ndhc/state.c
+++ b/ndhc/state.c
@@ -13,9 +13,9 @@
 #include "random.h"
 
 static void selecting_packet(struct client_state_t *cs, struct dhcpmsg *packet,
-                             uint8_t *message);
+                             uint8_t msgtype);
 static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
-                      uint8_t *message);
+                      uint8_t msgtype);
 static void selecting_timeout(struct client_state_t *cs, long long nowts);
 static void requesting_timeout(struct client_state_t *cs, long long nowts);
 static void bound_timeout(struct client_state_t *cs, long long nowts);
@@ -28,7 +28,7 @@ static void frenew(struct client_state_t *cs);
 
 typedef struct {
     void (*packet_fn)(struct client_state_t *cs, struct dhcpmsg *packet,
-                      uint8_t *message);
+                      uint8_t msgtype);
     void (*timeout_fn)(struct client_state_t *cs, long long nowts);
     void (*force_renew_fn)(struct client_state_t *cs);
     void (*force_release_fn)(struct client_state_t *cs);
@@ -186,9 +186,9 @@ static int validate_serverid(struct client_state_t *cs, struct dhcpmsg *packet,
 
 // Can transition to DS_BOUND or DS_SELECTING.
 static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
-                      uint8_t *message)
+                      uint8_t msgtype)
 {
-    if (*message == DHCPACK) {
+    if (msgtype == DHCPACK) {
         if (!validate_serverid(cs, packet, "a DHCP ACK"))
             return;
         ssize_t optlen;
@@ -230,7 +230,7 @@ static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
             set_listen_none(cs);
         }
 
-    } else if (*message == DHCPNAK) {
+    } else if (msgtype == DHCPNAK) {
         if (!validate_serverid(cs, packet, "a DHCP NAK"))
             return;
         log_line("Our request was rejected.  Searching for a new lease...");
@@ -239,9 +239,9 @@ static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
 }
 
 static void selecting_packet(struct client_state_t *cs, struct dhcpmsg *packet,
-                             uint8_t *message)
+                             uint8_t msgtype)
 {
-    if (*message == DHCPOFFER) {
+    if (msgtype == DHCPOFFER) {
         uint8_t *temp = NULL;
         ssize_t optlen;
         if ((temp = get_option_data(packet, DHCP_SERVER_ID, &optlen))) {
@@ -351,10 +351,10 @@ void ifnocarrier_action(struct client_state_t *cs)
 }
 
 void packet_action(struct client_state_t *cs, struct dhcpmsg *packet,
-                   uint8_t *message)
+                   uint8_t msgtype)
 {
     if (dhcp_states[cs->dhcpState].packet_fn)
-        dhcp_states[cs->dhcpState].packet_fn(cs, packet, message);
+        dhcp_states[cs->dhcpState].packet_fn(cs, packet, msgtype);
 }
 
 void timeout_action(struct client_state_t *cs, long long nowts)
diff --git a/ndhc/state.h b/ndhc/state.h
index ab86e7f..3ba5f16 100644
--- a/ndhc/state.h
+++ b/ndhc/state.h
@@ -19,7 +19,7 @@ typedef enum {
 void reinit_selecting(struct client_state_t *cs, int timeout);
 
 void packet_action(struct client_state_t *cs, struct dhcpmsg *packet,
-                   uint8_t *message);
+                   uint8_t msgtype);
 void timeout_action(struct client_state_t *cs, long long nowts);
 void force_renew_action(struct client_state_t *cs);
 void force_release_action(struct client_state_t *cs);