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Add dhcp_snprintf() for extracting DHCP string options.

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This commit is contained in:
Michael Brown 2006-07-20 14:13:11 +00:00
parent 7ca8bcd98c
commit b26806cf18
2 changed files with 44 additions and 0 deletions
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10
src/include/gpxe/dhcp.h
View File

@ -160,6 +160,13 @@
*/
#define DHCP_EB_SIADDR DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 3 )
/** BIOS drive number
*
* This is the drive number for a drive emulated via INT 13. 0x80 is
* the first hard disk, 0x81 is the second hard disk, etc.
*/
#define DHCP_EB_BIOS_DRIVE DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbd )
/** Maximum normal DHCP option */
#define DHCP_MAX_OPTION 254
@ -255,6 +262,7 @@ struct dhcp_option {
uint32_t dword;
struct in_addr in;
uint8_t bytes[0];
char string[0];
} data;
} __attribute__ (( packed ));
@ -435,6 +443,8 @@ struct dhcp_session {
extern unsigned long dhcp_num_option ( struct dhcp_option *option );
extern void dhcp_ipv4_option ( struct dhcp_option *option,
struct in_addr *inp );
extern int dhcp_snprintf ( char *buf, size_t size,
struct dhcp_option *option );
extern struct dhcp_option *
find_dhcp_option ( struct dhcp_option_block *options, unsigned int tag );
extern void register_dhcp_options ( struct dhcp_option_block *options );

34
src/net/dhcpopts.c
View File

@ -101,6 +101,40 @@ void dhcp_ipv4_option ( struct dhcp_option *option, struct in_addr *inp ) {
*inp = option->data.in;
}
/**
* Print DHCP string option value into buffer
*
* @v buf Buffer into which to write the string
* @v size Size of buffer
* @v option DHCP option, or NULL
* @ret len Length of formatted string
*
* DHCP option strings are stored without a NUL terminator. This
* function provides a convenient way to extract these DHCP strings
* into standard C strings. It is permitted to call dhcp_snprintf()
* with @c option set to NULL; in this case the buffer will be filled
* with an empty string.
*
* The usual snprintf() semantics apply with regard to buffer size,
* return value when the buffer is too small, etc.
*/
int dhcp_snprintf ( char *buf, size_t size, struct dhcp_option *option ) {
size_t len;
char *content = "";
if ( option ) {
/* Shrink buffer size so that it is only just large
* enough to contain the option data. snprintf() will
* take care of everything else (inserting the NUL etc.)
*/
len = ( option->len + 1 );
if ( len < size )
size = len;
content = option->data.string;
}
return snprintf ( buf, size, "%s", content );
}
/**
* Calculate length of a normal DHCP option
*