[SLOF] [PATCH 6/7] net-snk: Use transaction IDs in DHCPv4, too

[Stefan Berger]

On 12/17/2015 03:18 PM, Thomas Huth wrote:
> Generate a proper transaction ID before sending DHCPv4 packets
> and check whether the DHCPv4 replies contain that correct XID, too.
>
> Signed-off-by: Thomas Huth <thuth at redhat.com>
> ---
>   clients/net-snk/app/netapps/netboot.c |  2 ++
>   clients/net-snk/app/netlib/dhcp.c     | 17 +++++++++++++++--
>   clients/net-snk/app/netlib/dhcp.h     |  1 +
>   3 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/clients/net-snk/app/netapps/netboot.c b/clients/net-snk/app/netapps/netboot.c
> index d51d5a8..9f5ff8d 100644
> --- a/clients/net-snk/app/netapps/netboot.c
> +++ b/clients/net-snk/app/netapps/netboot.c
> @@ -332,6 +332,8 @@ int dhcp(char *ret_buffer, filename_ip_t * fn_ip, unsigned int retries, int flag
>   	int i = (int) retries+1;
>   	int rc = -1;
>   
> +	if (flags != F_IPV6)
> +		dhcpv4_generate_transaction_id();

Same comment as before. flags == F_IPV4?

>   	if (flags != F_IPV4)
>   		dhcpv6_generate_transaction_id();
>   
> diff --git a/clients/net-snk/app/netlib/dhcp.c b/clients/net-snk/app/netlib/dhcp.c
> index 5f26f3a..bd9c104 100644
> --- a/clients/net-snk/app/netlib/dhcp.c
> +++ b/clients/net-snk/app/netlib/dhcp.c
> @@ -178,11 +178,18 @@ static uint32_t dhcp_server_ip     = 0;
>   static uint32_t dhcp_siaddr_ip     = 0;
>   static int8_t   dhcp_filename[256];
>   static int8_t   dhcp_tftp_name[256];
> +static uint32_t dhcp_xid;
>   
>   static char   * response_buffer;
>   
>   /*>>>>>>>>>>>>>>>>>>>>>>>>>>>> IMPLEMENTATION <<<<<<<<<<<<<<<<<<<<<<<<<<<*/
>   
> +void
> +dhcpv4_generate_transaction_id(void)
> +{
> +	dhcp_xid = (rand() << 16) ^ rand();
> +}
> +
>   int32_t
>   dhcpv4(char *ret_buffer, filename_ip_t * fn_ip) {
>   
> @@ -627,6 +634,7 @@ dhcp_send_discover(int fd) {
>   	btph -> op = 1;
>   	btph -> htype = 1;
>   	btph -> hlen = 6;
> +	btph -> xid = dhcp_xid;
>   	memcpy(btph -> chaddr, get_mac_address(), 6);
>   
>   	memset(&opt, 0, sizeof(dhcp_options_t));
> @@ -670,6 +678,7 @@ dhcp_send_request(int fd) {
>   	btph -> op = 1;
>   	btph -> htype = 1;
>   	btph -> hlen = 6;
> +	btph -> xid = dhcp_xid;
>   	memcpy(btph -> chaddr, get_mac_address(), 6);
>   
>   	memset(&opt, 0, sizeof(dhcp_options_t));
> @@ -718,6 +727,7 @@ void dhcp_send_release(int fd) {
>   	btph -> op = 1;
>   	btph -> htype = 1;
>   	btph -> hlen = 6;
> +	btph -> xid = dhcp_xid;
>   	strcpy((char *) btph -> file, "");
>   	memcpy(btph -> chaddr, get_mac_address(), 6);
>   	btph -> ciaddr = htonl(dhcp_own_ip);
> @@ -763,8 +773,11 @@ handle_dhcp(int fd, uint8_t * packet, int32_t packetsize) {
>   	btph = (struct btphdr *) packet;
>   	iph = (struct iphdr *) packet - sizeof(struct udphdr) -
>   	      sizeof(struct iphdr);
> -	if (btph -> op != 2)
> -		return -1; // it is not Boot Reply
> +
> +	if (btph->op != 2)
> +		return -1;		/* It is not a Bootp/DHCP reply */
> +	if (btph->xid != dhcp_xid)
> +		return -1;		/* The transaction ID does not match */
>   
>   	if (memcmp(btph -> vend, dhcp_magic, 4)) {
>   		// It is BootP - RFC 951
> diff --git a/clients/net-snk/app/netlib/dhcp.h b/clients/net-snk/app/netlib/dhcp.h
> index 69dd49d..54fb1ee 100644
> --- a/clients/net-snk/app/netlib/dhcp.h
> +++ b/clients/net-snk/app/netlib/dhcp.h
> @@ -43,6 +43,7 @@ struct btphdr {
>   	uint8_t vend[64];    /**< Optional parameters field (DHCP-options)     */
>   };
>   
> +void dhcpv4_generate_transaction_id(void);
>   int bootp(char *ret_buffer, filename_ip_t *, unsigned int);
>   int dhcpv4(char *ret_buffer, filename_ip_t *);
>   void dhcp_send_release(int fd);
Rest looks good.

    Stefan