Re: [PATCH] net: dhcp: allow to set transmitted vendor id

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Mar 06, 2012 at 06:36:15PM +0100, Enrico Scholz wrote:
> For net boot setups it is useful to submit boot params like server or
> bootfile over dhcp.  To distinguish barebox from e.g. pxe machines, a
> custom vendor id can be sent in dhcp discover/request messages.
> 
> E.g. the ISC dhcp server can be configured with
> 
> | if substring(option vendor-class-identifier,0,8) = "barebox:" {
> | 	next-server		192.168.3.24;
> | 	server-name		"192.168.3.24";
> | 	option tftp-server-name	"192.168.3.24";
> | 	option root-path = concat("/srv/sysroots/by-mac/",
> |          binary-to-ascii (16, 8, "-", substring (hardware, 1, 6)));
> | }
> 
> to sent boot params which are valid for barebox hosts only.

I like this one aswell. The string shouldn't be hardcoded though.
It could be a command line option to dhcp.

Sascha

> 
> Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
> ---
>  net/Kconfig |   13 +++++++++++++
>  net/dhcp.c  |   12 ++++++++++++
>  2 files changed, 25 insertions(+), 0 deletions(-)
> 
> diff --git a/net/Kconfig b/net/Kconfig
> index 3169d20..56d6ee8 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -7,6 +7,19 @@ config NET_DHCP
>  	bool
>  	prompt "dhcp support"
>  
> +config NET_DHCP_VENDOR_ID
> +        string
> +	prompt "dhcp vendor id"
> +	depends on NET_DHCP
> +	default "barebox:default"
> +	help
> +	  DHCP Vendor ID (code 60) submitted in DHCP requests. It can
> +	  be used in the DHCP server's configuration to select options
> +	  (e.g. bootfile or server) which are valid for barebox clients
> +	  only.
> +
> +	  An empty string will suppress generation of such requests.
> +
>  config NET_NFS
>  	bool
>  	prompt "nfs support"
> diff --git a/net/dhcp.c b/net/dhcp.c
> index 2ce9090..65f2614 100644
> --- a/net/dhcp.c
> +++ b/net/dhcp.c
> @@ -129,6 +129,7 @@ static void bootp_copy_net_params(struct bootp *bp)
>   */
>  static int dhcp_extended (u8 *e, int message_type, IPaddr_t ServerID, IPaddr_t RequestedIP)
>  {
> +	size_t vendor_id_len = sizeof CONFIG_NET_DHCP_VENDOR_ID - 1;
>  	u8 *start = e;
>  	u8 *cnt;
>  
> @@ -168,6 +169,17 @@ static int dhcp_extended (u8 *e, int message_type, IPaddr_t ServerID, IPaddr_t R
>  		*e++ = tmp & 0xff;
>  	}
>  
> +	/* 64 is some arbitrary value to prevent generation of too
> +	 * large dhcp requests. */
> +	BUILD_BUG_ON(sizeof CONFIG_NET_DHCP_VENDOR_ID > 64);
> +
> +	if (vendor_id_len > 0) {
> +		*e++ = 60;
> +		*e++ = vendor_id_len;
> +		memcpy(e, CONFIG_NET_DHCP_VENDOR_ID,  vendor_id_len);
> +		e   += vendor_id_len;
> +	}
> +
>  	*e++ = 55;		/* Parameter Request List */
>  	 cnt = e++;		/* Pointer to count of requested items */
>  	*cnt = 0;
> -- 
> 1.7.7.6
> 
> 
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