From b26806cf182e67e759511ccc95e50fb165f305c9 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Thu, 20 Jul 2006 14:13:11 +0000 Subject: [PATCH] Add dhcp_snprintf() for extracting DHCP string options. --- src/include/gpxe/dhcp.h | 10 ++++++++++ src/net/dhcpopts.c | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 44 insertions(+) diff --git a/src/include/gpxe/dhcp.h b/src/include/gpxe/dhcp.h index 51fd8195..5f1943eb 100644 --- a/src/include/gpxe/dhcp.h +++ b/src/include/gpxe/dhcp.h @@ -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 ); diff --git a/src/net/dhcpopts.c b/src/net/dhcpopts.c index ebd6de75..c906b191 100644 --- a/src/net/dhcpopts.c +++ b/src/net/dhcpopts.c @@ -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 *