add compile-time check for correct DHCP packet size

1 files changed, 4 insertions, 0 deletions

diff --git a/networking/udhcp/packet.c b/networking/udhcp/packet.c
index e79542d08..85910447b 100644
--- a/networking/udhcp/packet.c
+++ b/networking/udhcp/packet.c
@@ -109,6 +109,7 @@ uint16_t udhcp_checksum(void *addr, int count)
 
 
 /* Construct a ip/udp header for a packet, and specify the source and dest hardware address */
+void BUG_sizeof_struct_udp_dhcp_packet_must_be_576(void);
 int udhcp_raw_packet(struct dhcpMessage *payload,
                 uint32_t source_ip, int source_port,
                 uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex)
@@ -154,6 +155,9 @@ int udhcp_raw_packet(struct dhcpMessage *payload,
         packet.ip.ttl = IPDEFTTL;
         packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));
 
+        if (sizeof(struct udp_dhcp_packet) != 576)
+                BUG_sizeof_struct_udp_dhcp_packet_must_be_576();
+
         result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0,
                         (struct sockaddr *) &dest, sizeof(dest));
         if (result <= 0) {