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[dhcp] Allow use of custom reallocation functions for DHCP option blocks
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Allow functions other than realloc() to be used to reallocate DHCP
option block data, and specify the reallocation function at the time
of calling dhcpopt_init().

Signed-off-by: Michael Brown <mcb30@ipxe.org>
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@mcb30
mcb30 committed Jan 11, 2011
1 parent 310d46c commit 17b6a3c
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Showing 4 changed files with 74 additions and 62 deletions.
3 changes: 2 additions & 1 deletion src/core/nvo.c
View file
Expand Up @@ -133,7 +133,8 @@ static void nvo_init_dhcpopts ( struct nvo_block *nvo ) {
memset ( nvo->data, 0, nvo->total_len );
}

dhcpopt_init ( &nvo->dhcpopts, options_data, options_len );
dhcpopt_init ( &nvo->dhcpopts, options_data, options_len,
dhcpopt_no_realloc );
}

/**
Expand Down
15 changes: 11 additions & 4 deletions src/include/ipxe/dhcpopts.h
View file
Expand Up @@ -19,16 +19,23 @@ struct dhcp_options {
size_t used_len;
/** Option block allocated length */
size_t alloc_len;
/** Reallocate option block raw data
*
* @v options DHCP option block
* @v len New length
* @ret rc Return status code
*/
int ( * realloc ) ( struct dhcp_options *options, size_t len );
};

extern int dhcpopt_store ( struct dhcp_options *options, unsigned int tag,
const void *data, size_t len );
extern int dhcpopt_extensible_store ( struct dhcp_options *options,
unsigned int tag,
const void *data, size_t len );
extern int dhcpopt_fetch ( struct dhcp_options *options, unsigned int tag,
void *data, size_t len );
extern void dhcpopt_init ( struct dhcp_options *options,
void *data, size_t alloc_len );
void *data, size_t alloc_len,
int ( * realloc ) ( struct dhcp_options *options,
size_t len ) );
extern int dhcpopt_no_realloc ( struct dhcp_options *options, size_t len );

#endif /* _IPXE_DHCPOPTS_H */
115 changes: 59 additions & 56 deletions src/net/dhcpopts.c
View file
Expand Up @@ -169,6 +169,17 @@ static int find_dhcp_option_with_encap ( struct dhcp_options *options,
return -ENOENT;
}

/**
* Refuse to reallocate DHCP option block
*
* @v options DHCP option block
* @v len New length
* @ret rc Return status code
*/
int dhcpopt_no_realloc ( struct dhcp_options *options, size_t len ) {
return ( ( len <= options->alloc_len ) ? 0 : -ENOSPC );
}

/**
* Resize a DHCP option
*
Expand All @@ -177,46 +188,44 @@ static int find_dhcp_option_with_encap ( struct dhcp_options *options,
* @v encap_offset Offset of encapsulating offset (or -ve for none)
* @v old_len Old length (including header)
* @v new_len New length (including header)
* @v can_realloc Can reallocate options data if necessary
* @ret rc Return status code
*/
static int resize_dhcp_option ( struct dhcp_options *options,
int offset, int encap_offset,
size_t old_len, size_t new_len,
int can_realloc ) {
size_t old_len, size_t new_len ) {
struct dhcp_option *encapsulator;
struct dhcp_option *option;
ssize_t delta = ( new_len - old_len );
size_t new_options_len;
size_t old_alloc_len;
size_t new_used_len;
size_t new_encapsulator_len;
void *new_data;
void *source;
void *dest;
void *end;
int rc;

/* Check for sufficient space, and update length fields */
/* Check for sufficient space */
if ( new_len > DHCP_MAX_LEN ) {
DBGC ( options, "DHCPOPT %p overlength option\n", options );
return -ENOSPC;
}
new_options_len = ( options->used_len + delta );
if ( new_options_len > options->alloc_len ) {
/* Reallocate options block if allowed to do so. */
if ( can_realloc ) {
new_data = realloc ( options->data, new_options_len );
if ( ! new_data ) {
DBGC ( options, "DHCPOPT %p could not "
"reallocate to %zd bytes\n", options,
new_options_len );
return -ENOMEM;
}
options->data = new_data;
options->alloc_len = new_options_len;
} else {
DBGC ( options, "DHCPOPT %p out of space\n", options );
return -ENOMEM;
new_used_len = ( options->used_len + delta );

/* Expand options block, if necessary */
if ( new_used_len > options->alloc_len ) {
/* Reallocate options block */
old_alloc_len = options->alloc_len;
if ( ( rc = options->realloc ( options, new_used_len ) ) != 0 ){
DBGC ( options, "DHCPOPT %p could not reallocate to "
"%zd bytes\n", options, new_used_len );
return rc;
}
/* Clear newly allocated space */
memset ( ( options->data + old_alloc_len ), 0,
( options->alloc_len - old_alloc_len ) );
}

/* Update encapsulator, if applicable */
if ( encap_offset >= 0 ) {
encapsulator = dhcp_option ( options, encap_offset );
new_encapsulator_len = ( encapsulator->len + delta );
Expand All @@ -227,7 +236,9 @@ static int resize_dhcp_option ( struct dhcp_options *options,
}
encapsulator->len = new_encapsulator_len;
}
options->used_len = new_options_len;

/* Update used length */
options->used_len = new_used_len;

/* Move remainder of option data */
option = dhcp_option ( options, offset );
Expand All @@ -236,6 +247,15 @@ static int resize_dhcp_option ( struct dhcp_options *options,
end = ( options->data + options->alloc_len );
memmove ( dest, source, ( end - dest ) );

/* Shrink options block, if applicable */
if ( new_used_len < options->alloc_len ) {
if ( ( rc = options->realloc ( options, new_used_len ) ) != 0 ){
DBGC ( options, "DHCPOPT %p could not reallocate to "
"%zd bytes\n", options, new_used_len );
return rc;
}
}

return 0;
}

Expand All @@ -246,7 +266,6 @@ static int resize_dhcp_option ( struct dhcp_options *options,
* @v tag DHCP option tag
* @v data New value for DHCP option
* @v len Length of value, in bytes
* @v can_realloc Can reallocate options data if necessary
* @ret offset Offset of DHCP option, or negative error
*
* Sets the value of a DHCP option within the options block. The
Expand All @@ -258,9 +277,8 @@ static int resize_dhcp_option ( struct dhcp_options *options,
* be left with its original value.
*/
static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,
const void *data, size_t len,
int can_realloc ) {
static const uint8_t empty_encapsulator[] = { DHCP_END };
const void *data, size_t len ) {
static const uint8_t empty_encap[] = { DHCP_END };
int offset;
int encap_offset = -1;
int creation_offset;
Expand Down Expand Up @@ -291,10 +309,12 @@ static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,

/* Ensure that encapsulator exists, if required */
if ( encap_tag ) {
if ( encap_offset < 0 )
encap_offset = set_dhcp_option ( options, encap_tag,
empty_encapsulator, 1,
can_realloc );
if ( encap_offset < 0 ) {
encap_offset =
set_dhcp_option ( options, encap_tag,
empty_encap,
sizeof ( empty_encap ) );
}
if ( encap_offset < 0 )
return encap_offset;
creation_offset = ( encap_offset + DHCP_OPTION_HEADER_LEN );
Expand All @@ -306,8 +326,7 @@ static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,

/* Resize option to fit new data */
if ( ( rc = resize_dhcp_option ( options, offset, encap_offset,
old_len, new_len,
can_realloc ) ) != 0 )
old_len, new_len ) ) != 0 )
return rc;

/* Copy new data into option, if applicable */
Expand All @@ -322,7 +341,7 @@ static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,
if ( encap_offset >= 0 ) {
option = dhcp_option ( options, encap_offset );
if ( option->len <= 1 )
set_dhcp_option ( options, encap_tag, NULL, 0, 0 );
set_dhcp_option ( options, encap_tag, NULL, 0 );
}

return offset;
Expand All @@ -341,26 +360,7 @@ int dhcpopt_store ( struct dhcp_options *options, unsigned int tag,
const void *data, size_t len ) {
int offset;

offset = set_dhcp_option ( options, tag, data, len, 0 );
if ( offset < 0 )
return offset;
return 0;
}

/**
* Store value of DHCP option setting, extending options block if necessary
*
* @v options DHCP option block
* @v tag Setting tag number
* @v data Setting data, or NULL to clear setting
* @v len Length of setting data
* @ret rc Return status code
*/
int dhcpopt_extensible_store ( struct dhcp_options *options, unsigned int tag,
const void *data, size_t len ) {
int offset;

offset = set_dhcp_option ( options, tag, data, len, 1 );
offset = set_dhcp_option ( options, tag, data, len );
if ( offset < 0 )
return offset;
return 0;
Expand Down Expand Up @@ -428,16 +428,19 @@ static void dhcpopt_update_used_len ( struct dhcp_options *options ) {
* @v options Uninitialised DHCP option block
* @v data Memory for DHCP option data
* @v alloc_len Length of memory for DHCP option data
* @v realloc DHCP option block reallocator
*
* The memory content must already be filled with valid DHCP options.
* A zeroed block counts as a block of valid DHCP options.
*/
void dhcpopt_init ( struct dhcp_options *options, void *data,
size_t alloc_len ) {
void dhcpopt_init ( struct dhcp_options *options, void *data, size_t alloc_len,
int ( * realloc ) ( struct dhcp_options *options,
size_t len ) ) {

/* Fill in fields */
options->data = data;
options->alloc_len = alloc_len;
options->realloc = realloc;

/* Update length */
dhcpopt_update_used_len ( options );
Expand Down
3 changes: 2 additions & 1 deletion src/net/dhcppkt.c
View file
Expand Up @@ -267,7 +267,8 @@ void dhcppkt_init ( struct dhcp_packet *dhcppkt, struct dhcphdr *data,
ref_init ( &dhcppkt->refcnt, NULL );
dhcppkt->dhcphdr = data;
dhcpopt_init ( &dhcppkt->options, &dhcppkt->dhcphdr->options,
( len - offsetof ( struct dhcphdr, options ) ) );
( len - offsetof ( struct dhcphdr, options ) ),
dhcpopt_no_realloc );
settings_init ( &dhcppkt->settings,
&dhcppkt_settings_operations, &dhcppkt->refcnt, 0 );
}

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