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[dhcp] Append new DHCP options versus prepend

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Change the behaviour for adding DHCP options into a DHCP packet so
that we now append options, rather than insert them in front of
whatever options might already be present.

Apparently, the DHCP relay logic on a Nortel 470-48T layer 2 switch
cares about the order of DHCP options.  If we build a DHCP packet
pre-populated with some options, their order will now be preserved,
except for encapsulated options.

Signed-off-by: Marty Connor <mdc@etherboot.org>
This commit is contained in:
Shao Miller 2009-10-22 16:51:43 -04:00 committed by Marty Connor
parent 9de525c34c
commit cf5e79adc9
1 changed files with 15 additions and 4 deletions
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19
src/net/dhcpopts.c
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@ -103,7 +103,7 @@ static unsigned int dhcp_option_len ( struct dhcp_option *option ) {
* DHCP option block. Encapsulated options may be searched for by
* using DHCP_ENCAP_OPT() to construct the tag value.
*
* If the option is encapsulated, and @c encapsulator is non-NULL, it
* If the option is encapsulated, and @c encap_offset is non-NULL, it
* will be filled in with the offset of the encapsulating option.
*
* This routine is designed to be paranoid. It does not assume that
@ -136,8 +136,15 @@ static int find_dhcp_option_with_encap ( struct dhcp_options *options,
if ( remaining < 0 )
break;
/* Check for explicit end marker */
if ( option->tag == DHCP_END )
break;
if ( option->tag == DHCP_END ) {
if ( tag == DHCP_END )
/* Special case where the caller is interested
* in whether we have this marker or not.
*/
return offset;
else
break;
}
/* Check for matching tag */
if ( option->tag == tag ) {
DBGC ( options, "DHCPOPT %p found %s (length %d)\n",
@ -256,7 +263,7 @@ static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,
static const uint8_t empty_encapsulator[] = { DHCP_END };
int offset;
int encap_offset = -1;
int creation_offset = 0;
int creation_offset;
struct dhcp_option *option;
unsigned int encap_tag = DHCP_ENCAPSULATOR ( tag );
size_t old_len = 0;
@ -267,6 +274,10 @@ static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,
if ( tag == DHCP_PAD )
return -ENOTTY;
creation_offset = find_dhcp_option_with_encap ( options, DHCP_END,
NULL );
if ( creation_offset < 0 )
creation_offset = options->len;
/* Find old instance of this option, if any */
offset = find_dhcp_option_with_encap ( options, tag, &encap_offset );
if ( offset >= 0 ) {