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dhcp.c File Reference
`#include "lwip/opt.h"`
`#include "lwip/stats.h"`
`#include "lwip/mem.h"`
`#include "lwip/udp.h"`
`#include "lwip/ip_addr.h"`
`#include "lwip/netif.h"`
`#include "lwip/def.h"`
`#include "lwip/dhcp.h"`
`#include "lwip/autoip.h"`
`#include "lwip/acd.h"`
`#include "lwip/dns.h"`
`#include "lwip/etharp.h"`
`#include "lwip/prot/dhcp.h"`
`#include "lwip/prot/iana.h"`
`#include <string.h>`
`#include "path/to/my/lwip_hooks.h"`

## Macros

#define | DHCP_ADD_EXTRA_REQUEST_OPTIONS
#define | SET_TIMEOUT_FROM_OFFERED(result, offered, min, max)
#define | DHCP_CREATE_RAND_XID 1
#define | DHCP_MAX_MSG_LEN(netif)
#define | DHCP_MIN_REPLY_LEN 44

## Enumerations

enum | dhcp_option_idx

## Functions

void | dhcp_coarse_tmr (void)
void | dhcp_fine_tmr (void)
void | dhcp_set_struct (struct netif *netif, struct dhcp *dhcp)
void | dhcp_cleanup (struct netif *netif)
err_t | dhcp_start (struct netif *netif)
void | dhcp_inform (struct netif *netif)
void | dhcp_network_changed_link_up (struct netif *netif)
err_t | dhcp_renew (struct netif *netif)
void | dhcp_release_and_stop (struct netif *netif)
err_t | dhcp_release (struct netif *netif)
void | dhcp_stop (struct netif *netif)
u8_t | dhcp_supplied_address (const struct netif *netif)

## Detailed Description

Dynamic Host Configuration Protocol client

## Macro Definition Documentation

## DHCP_ADD_EXTRA_REQUEST_OPTIONS

#define DHCP_ADD_EXTRA_REQUEST_OPTIONS

DHCP_ADD_EXTRA_REQUEST_OPTIONS: Additional options added to the list of options that the client requests from the servers (opt 55: DHCP_OPTION_PARAMETER_REQUEST_LIST) If additional options are requested, define this macro as a comma separated list, with leading comma. This macro is useful for example when requested vendor specific ids (VCI/VSI options), here is an example of requesting the VSI option (option 43) (yes, the notation is a bit strange, but it works :) (NOTE: the space between # and define is required because of doxygen...)

# define DHCP_ADD_EXTRA_REQUEST_OPTIONS ,43

## DHCP_CREATE_RAND_XID

#define DHCP_CREATE_RAND_XID 1

DHCP_CREATE_RAND_XID: if this is set to 1, the xid is created using LWIP_RAND() (this overrides DHCP_GLOBAL_XID)

## DHCP_MAX_MSG_LEN

#define DHCP_MAX_MSG_LEN | ( |  | netif | ) |

Value:
(netif->mtu)
netif
Definition netif.h:269
netif::mtu
u16_t mtu
Definition netif.h:344

Default for DHCP_GLOBAL_XID is 0xABCD0000 This can be changed by defining DHCP_GLOBAL_XID and DHCP_GLOBAL_XID_HEADER, e.g. #define DHCP_GLOBAL_XID_HEADER "stdlib.h" #define DHCP_GLOBAL_XID rand() DHCP_OPTION_MAX_MSG_SIZE is set to the MTU MTU is checked to be big enough in dhcp_start

## DHCP_MIN_REPLY_LEN

#define DHCP_MIN_REPLY_LEN 44

Minimum length for reply before packet is parsed

## SET_TIMEOUT_FROM_OFFERED

#define SET_TIMEOUT_FROM_OFFERED | ( |  | result,
|  |  | offered,
|  |  | min,
|  |  | max )

Value:
do { \
u32_t timeout = (offered + DHCP_COARSE_TIMER_SECS / 2) / DHCP_COARSE_TIMER_SECS; \
if (timeout > max) { \
timeout = max; \
} \
if (timeout == min) { \
timeout = 1; \
} \
result = (dhcp_timeout_t)timeout; \
} while(0)
DHCP_COARSE_TIMER_SECS
#define DHCP_COARSE_TIMER_SECS
Definition dhcp.h:65
dhcp_timeout_t
u16_t dhcp_timeout_t
Definition dhcp.h:61

DHCP_DEFINE_CUSTOM_TIMEOUTS: if this is defined then you can customize various DHCP timeouts using these macros:

- DHCP_SET_TIMEOUT_FROM_OFFERED_T0_LEASE() to adjust the t0 lease timeout from the offered value
- DHCP_SET_TIMEOUT_FROM_OFFERED_T1_RENEW() same for t1 renew
- DHCP_SET_TIMEOUT_FROM_OFFERED_T2_REBIND() same for t2 rebind
- DHCP_NEXT_TIMEOUT_THRESHOLD to adjust the period of the next timeout
- DHCP_REQUEST_BACKOFF_SEQUENCE to adjust back-off times based on DHCP request attempts

## Enumeration Type Documentation

## dhcp_option_idx

enum dhcp_option_idx

Option handling: options are parsed in dhcp_parse_reply and saved in an array where other functions can load them from. This might be moved into the struct dhcp (not necessarily since lwIP is single-threaded and the array is only used while in recv callback).

## Function Documentation

## dhcp_coarse_tmr()

void dhcp_coarse_tmr | ( | void |  | ) |

The DHCP timer that checks for lease renewal/rebind timeouts. Must be called once a minute (see DHCP_COARSE_TIMER_SECS).

## dhcp_fine_tmr()

void dhcp_fine_tmr | ( | void |  | ) |

DHCP transaction timeout handling (this function must be called every 500ms, see DHCP_FINE_TIMER_MSECS).

A DHCP server is expected to respond within a short period of time. This timer checks whether an outstanding DHCP request is timed out.

## dhcp_network_changed_link_up()

void dhcp_network_changed_link_up | ( | struct netif * | netif | ) |

Handle a possible change in the network configuration.

This enters the REBOOTING state to verify that the currently bound address is still valid.

## dhcp_supplied_address()

u8_t dhcp_supplied_address | ( | const struct netif * | netif | ) |

check if DHCP supplied netif->ip_addr

Parameters

  netif | the netif to check

Returns
  1 if DHCP supplied netif->ip_addr (states BOUND or RENEWING), 0 otherwise