lwIP

https://www.nongnu.org/lwip/2_1_x/
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### mem_init()

Source: https://www.nongnu.org/lwip/2_1_x/mem_8c.html

Initializes the heap by zeroing it and setting up the start, end, and lowest-free pointers.

```APIDOC
## mem_init()

### Description
Zero the heap and initialize start, end and lowest-free.

### Method
mem_init

### Signature
void mem_init(void)

### Parameters
None

### Returns
None

```

--------------------------------

### autoip_start

Source: https://www.nongnu.org/lwip/2_1_x/autoip_8c.html

Starts the AutoIP process on a network interface.

```APIDOC
## autoip_start

### Description
Starts the AutoIP process on a network interface.

### Function Signature
err_t autoip_start(struct netif *netif)

### Parameters
- **netif** (struct netif *) - Required - The network interface on which to start AutoIP.

### Return Value
err_t - Error code indicating success or failure.
```

--------------------------------

### Raw API PPP example: globals and status callback

Source: https://www.nongnu.org/lwip/2_1_x/group__ppp.html

Shows the global PPP control block and netif declarations, plus a status callback that is invoked on PPP status changes from the lwIP core thread. The callback uses ppp_netif() to get the netif and ignores the ctx argument.

```c
/*
 * Globals
 * =======
 */

/* The PPP control block */
ppp_pcb *ppp;

/* The PPP IP interface */
struct netif ppp_netif;


/*
 * PPP status callback
 * ===================
 *
 * PPP status callback is called on PPP status change (up, down, …) from lwIP
 * core thread
 */

/* PPP status callback example */
static void status_cb(ppp_pcb *pcb, int err_code, void *ctx) {
  struct netif *pppif = ppp_netif(pcb);
  LWIP_UNUSED_ARG(ctx);

```

--------------------------------

### dhcp_start

Source: https://www.nongnu.org/lwip/2_1_x/dhcp_8h.html

Starts the DHCP client on a network interface.

```APIDOC
## dhcp_start

### Description
Starts the DHCP client on a network interface.

### Function Signature
err_t dhcp_start(struct netif *netif)

### Parameters
- **netif** (struct netif *) - Required - The network interface to start DHCP on.

### Returns
err_t - Error code indicating success or failure.
```

--------------------------------

### Zero-copy RX ethernet driver example (pbuf_custom, LWIP_MEMPOOL_DECLARE)

Source: https://www.nongnu.org/lwip/2_1_x/zerocopyrx.html

Complete zero-copy RX ethernet driver example from the lwIP documentation. It defines a custom pbuf struct with a DMA descriptor, declares a memory pool for these pbufs, implements the custom free function that invalidates the data cache and returns the descriptor, and shows the interrupt handler that allocates a pbuf from the pool, configures it, and feeds it to the network interface. Note the code uses the variable name 'my_puf' in the free function but 'my_pbuf' in the same function; this appears to be a typo in the original example.

```c
typedef struct my_custom_pbuf
{
struct pbuf_custom p;
void* dma_descriptor;
} my_custom_pbuf_t;
```

```c
LWIP_MEMPOOL_DECLARE(RX_POOL, 10, sizeof(my_custom_pbuf_t), "Zero-copy RX PBUF pool");
```

```c
void my_pbuf_free_custom(void* p)
{
SYS_ARCH_DECL_PROTECT(old_level);
my_custom_pbuf_t* my_puf = (my_custom_pbuf_t*)p;
// invalidate data cache here - lwIP and/or application may have written into buffer!
// (invalidate is faster than flushing, and noone needs the correct data in the buffer)
invalidate_cpu_cache(p->payload, p->tot_len);
SYS_ARCH_PROTECT(old_level);
free_rx_dma_descriptor(my_pbuf->dma_descriptor);
LWIP_MEMPOOL_FREE(RX_POOL, my_pbuf);
SYS_ARCH_UNPROTECT(old_level);
}
```

```c
void eth_rx_irq()
{
dma_descriptor* dma_desc = get_RX_DMA_descriptor_from_ethernet();
my_custom_pbuf_t* my_pbuf = (my_custom_pbuf_t*)LWIP_MEMPOOL_ALLOC(RX_POOL);
my_pbuf->p.custom_free_function = my_pbuf_free_custom;
my_pbuf->dma_descriptor = dma_desc;
invalidate_cpu_cache(dma_desc->rx_data, dma_desc->rx_length);
struct pbuf* p = pbuf_alloced_custom(PBUF_RAW,
dma_desc->rx_length,
PBUF_REF,
&my_pbuf->p,
dma_desc->rx_data,
dma_desc->max_buffer_size);
if(netif->input(p, netif) != ERR_OK) {
pbuf_free(p);
}
}
```

--------------------------------

### altcp_listen_with_backlog_and_err

Source: https://www.nongnu.org/lwip/2_1_x/altcp_8c.html

Starts listening on an altcp PCB with a specified backlog and error output.

```APIDOC
## altcp_listen_with_backlog_and_err

### Description
Starts listening on an altcp PCB with a specified backlog and error output.

### Function Signature
struct altcp_pcb *altcp_listen_with_backlog_and_err(struct altcp_pcb *conn, u8_t backlog, err_t *err)

### Parameters
- **conn** (struct altcp_pcb*) - Required - The altcp PCB to put into listening mode.
- **backlog** (u8_t) - Required - The maximum number of pending connections.
- **err** (err_t*) - Required - Pointer to store the error code if listening fails.

### Returns
- **struct altcp_pcb*** - Pointer to the listening PCB, or NULL on failure.
```

--------------------------------

### snmp_init

Source: https://www.nongnu.org/lwip/2_1_x/group__snmp__core.html

Starts the SNMP agent by allocating a UDP PCB and binding it to port 161.

```APIDOC
## snmp_init

### Description
Starts SNMP Agent. Allocates UDP pcb and binds it to IP_ANY_TYPE port 161. Agent setup, start listening to port 161.

### Method
void snmp_init(void)

### Parameters
None

### Returns
None
```

--------------------------------

### Establish connection with server using mqtt_client_connect

Source: https://www.nongnu.org/lwip/2_1_x/group__mqtt.html

Defines example_do_connect() which sets up a minimal client info structure, sets the client identifier, and calls mqtt_client_connect(). If the connection fails immediately, an error code is printed. The connection result is delivered via mqtt_connection_cb.

```c
void example_do_connect(mqtt_client_t *client)
{
  struct mqtt_connect_client_info_t ci;
  err_t err;
  
  /* Setup an empty client info structure */
  memset(&ci, 0, sizeof(ci));
  
  /* Minimal amount of information required is client identifier, so set it here */ 
  ci.client_id = "lwip_test";
  
  /* Initiate client and connect to server, if this fails immediately an error code is returned
     otherwise mqtt_connection_cb will be called with connection result after attempting 
     to establish a connection with the server. 
     For now MQTT version 3.1.1 is always used */
  
  err = mqtt_client_connect(client, ip_addr, MQTT_PORT, mqtt_connection_cb, 0, &ci);
  
  /* For now just print the result code if something goes wrong */
  if(err != ERR_OK) {
    printf("mqtt_connect return %d\n", err);
  }
}
```

--------------------------------

### httpc_get_file

Source: https://www.nongnu.org/lwip/2_1_x/group__httpc.html

Starts an HTTP GET request to a server specified by IP address.

```APIDOC
## httpc_get_file

### Description
Initiates an HTTP GET request to a server specified by IP address. The response is delivered via a callback function.

### Method
GET

### Endpoint
httpc_get_file

### Parameters
#### Function Parameters
- **server_addr** (const ip_addr_t *) - Required - IP address of the HTTP server
- **port** (u16_t) - Required - TCP port of the HTTP server
- **uri** (const char *) - Required - URI path to request
- **settings** (const httpc_connection_t *) - Required - Connection settings (e.g., proxy, use_proxy, altcp)
- **recv_fn** (altcp_recv_fn) - Required - Callback function for received data
- **callback_arg** (void *) - Required - Argument passed to the callback
- **connection** (httpc_state_t **) - Optional - Pointer to store the connection state

### Response
#### Return Value
- **err_t** - Error code indicating success or failure

```

--------------------------------

### httpc_get_file_dns

Source: https://www.nongnu.org/lwip/2_1_x/http__client_8c.html

Starts a HTTP GET request to the specified server name, resolving it via DNS. The response is delivered via the provided receive callback.

```APIDOC
## httpc_get_file_dns

### Description
Starts a HTTP GET request to the specified server name, resolving it via DNS. The response is delivered via the provided receive callback.

### Function Signature
err_t httpc_get_file_dns(const char *server_name, u16_t port, const char *uri, const httpc_connection_t *settings, altcp_recv_fn recv_fn, void *callback_arg, httpc_state_t **connection)

### Parameters
- **server_name** (const char *) - Required - Hostname of the server.
- **port** (u16_t) - Required - Port number of the server.
- **uri** (const char *) - Required - URI path to request.
- **settings** (const httpc_connection_t *) - Required - Connection settings (may be NULL for defaults).
- **recv_fn** (altcp_recv_fn) - Required - Callback function for received data.
- **callback_arg** (void *) - Required - Argument passed to the callback.
- **connection** (httpc_state_t **) - Required - Pointer to store the connection state.

### Return Value
err_t - Error code indicating success or failure.
```

--------------------------------

### httpd_inits()

Source: https://www.nongnu.org/lwip/2_1_x/group__httpd.html

Initializes the httpd with TLS support: sets up a listening PCB and binds it to the defined port, and also sets up TLS connection handling (HTTPS).

```APIDOC
## httpd_inits()

### Description
Initializes the httpd with TLS support: sets up a listening PCB and binds it to the defined port, and also sets up TLS connection handling (HTTPS).

### Method
Function

### Signature
void httpd_inits(struct altcp_tls_config *conf)

### Parameters
- **conf** (struct altcp_tls_config *) - Required - TLS configuration for HTTPS support.

### Returns
void
```

--------------------------------

### Publish example with callback

Source: https://www.nongnu.org/lwip/2_1_x/group__mqtt.html

Shows how to publish a message using mqtt_publish() with QoS 2 and retain flag 0. The callback mqtt_pub_request_cb is invoked when the publish completes, printing the result if an error occurs.

```c
void example_publish(mqtt_client_t *client, void *arg)
{
  const char *pub_payload= "PubSubHubLubJub";
  err_t err;
  u8_t qos = 2; /* 0 1 or 2, see MQTT specification */
  u8_t retain = 0; /* No don't retain such crappy payload... */
  err = mqtt_publish(client, "pub_topic", pub_payload, strlen(pub_payload), qos, retain, mqtt_pub_request_cb, arg);
  if(err != ERR_OK) {
    printf("Publish err: %d\n", err);
  }
}

/* Called when publish is complete either with sucess or failure */
static void mqtt_pub_request_cb(void *arg, err_t result)
{
  if(result != ERR_OK) {
    printf("Publish result: %d\n", result);
  }
}
```

--------------------------------

### httpd_init()

Source: https://www.nongnu.org/lwip/2_1_x/group__httpd.html

Initializes the httpd: sets up a listening PCB and binds it to the defined port. This function must be called before the HTTP server can accept connections.

```APIDOC
## httpd_init()

### Description
Initializes the httpd: sets up a listening PCB and binds it to the defined port. This function must be called before the HTTP server can accept connections.

### Method
Function

### Signature
void httpd_init(void)

### Parameters
None

### Returns
void
```

--------------------------------

### snmp_coldstart_trap

Source: https://www.nongnu.org/lwip/2_1_x/apps_2snmp_8h.html

Sends a cold start trap. This is a convenience function for sending a generic cold start trap.

```APIDOC
## snmp_coldstart_trap

### Description
Sends a cold start trap. This is a convenience function for sending a generic cold start trap.

### Method
void

### Signature
void snmp_coldstart_trap(void)

### Parameters
None

### Returns
None
```

--------------------------------

### dns_init

Source: https://www.nongnu.org/lwip/2_1_x/dns_8c.html

Initializes the DNS resolver by setting up the UDP PCB and configuring the default server if DNS_SERVER_ADDRESS is set.

```APIDOC
## dns_init

### Description
Initialize the resolver: set up the UDP pcb and configure the default server (if DNS_SERVER_ADDRESS is set).

### Function Signature
void dns_init(void)

### Parameters
None

### Returns
None
```

--------------------------------

### getsockopt()

Source: https://www.nongnu.org/lwip/2_1_x/group__socket.html

Gets socket options.

```APIDOC
## getsockopt()

### Description
Gets socket options.

### Function Signature
`getsockopt(s, level, optname, opval, optlen)`

### Parameters
- **s** (int) - Required - Socket descriptor.
- **level** (int) - Required - Protocol level (e.g., SOL_SOCKET).
- **optname** (int) - Required - Option name.
- **opval** (void*) - Required - Pointer to store the option value.
- **optlen** (socklen_t*) - Required - Pointer to the length of the option value.

### Returns
- **int** - 0 on success, or -1 on error.

### Notes
This is a macro that maps to `lwip_getsockopt`.
```

--------------------------------

### SMTP_BODYDH usage example

Source: https://www.nongnu.org/lwip/2_1_x/group__smtp.html

Shows how to use the SMTP_BODYDH feature to generate email body content dynamically. The callback function fills the buffer with lines and returns BDH_DONE when done. The example calls smtp_send_mail_bodycback with the callback.

```c
int my_smtp_bodydh_fn(void *arg, struct smtp_bodydh *bdh)
{
if(bdh->state >= 10) {
return BDH_DONE;
}
sprintf(bdh->buffer,"Line #%2d\r\n",bdh->state);
bdh->length = strlen(bdh->buffer);
++bdh->state;
return BDH_WORKING;
}
smtp_send_mail_bodycback("sender", "recipient", "subject", 
my_smtp_bodydh_fn, my_smtp_result_fn, some_argument);
```

--------------------------------

### getsockname()

Source: https://www.nongnu.org/lwip/2_1_x/group__socket.html

Gets the local address of a socket.

```APIDOC
## getsockname()

### Description
Gets the local address of a socket.

### Function Signature
`getsockname(s, name, namelen)`

### Parameters
- **s** (int) - Required - Socket descriptor.
- **name** (struct sockaddr*) - Required - Buffer to store the local address.
- **namelen** (socklen_t*) - Required - Pointer to the length of the address buffer.

### Returns
- **int** - 0 on success, or -1 on error.

### Notes
This is a macro that maps to `lwip_getsockname`.
```

--------------------------------

### sys_init()

Source: https://www.nongnu.org/lwip/2_1_x/group__sys__misc.html

Initializes the sys_arch layer. Must be called before anything else.

```APIDOC
## sys_init()

### Description
Initializes the sys_arch layer. Must be called before anything else.

### Method
Function

### Signature
void sys_init(void)

### Parameters
None

### Returns
None

```

--------------------------------

### httpd_init()

Source: https://www.nongnu.org/lwip/2_1_x/globals_h.html

Initializes the lwIP HTTP server. This function must be called to start the HTTP server.

```APIDOC
## httpd_init()

### Description
Initializes the lwIP HTTP server. This function must be called to start the HTTP server.

### Source
- httpd.h
- httpd.c

```

--------------------------------

### Initiate PPP client connection

Source: https://www.nongnu.org/lwip/2_1_x/group__ppp.html

Configures a PPP client session: sets it as default route, requests peer DNS, sets authentication, and initiates the connection with a holdoff of 0. Must be called when the session is in the dead state.

```c
/* Set this interface as default route */
ppp_set_default(ppp);

/* Ask the peer for up to 2 DNS server addresses. */
ppp_set_usepeerdns(ppp, 1);

/* Auth configuration, this is pretty self-explanatory */
ppp_set_auth(ppp, PPPAUTHTYPE_ANY, "login", "password");

/*
 * Initiate PPP negotiation, without waiting (holdoff=0), can only be called
 * if PPP session is in the dead state (i.e. disconnected).
 */
u16_t holdoff = 0;
ppp_connect(ppp, holdoff);
```

--------------------------------

### PPPoS session creation with output callback

Source: https://www.nongnu.org/lwip/2_1_x/group__ppp.html

Shows how to create a PPPoS (PPP over Serial) session. Includes the required include and an output callback that writes data to a UART. The pppos_create call uses the callback and a status callback.

```c
/*
 * Creating a new PPPoS session
 * ============================
 *
 * In lwIP, PPPoS is not PPPoSONET, in lwIP PPPoS is PPPoSerial.
 */

#include "netif/ppp/pppos.h"

/*
 * PPPoS serial output callback
 *
 * ppp_pcb, PPP control block
 * data, buffer to write to serial port
 * len, length of the data buffer
 * ctx, optional user-provided callback context pointer
 *
 * Return value: len if write succeed
 */
static u32_t output_cb(ppp_pcb *pcb, u8_t *data, u32_t len, void *ctx) {
  return uart_write(UART, data, len);
}

/*
 * Create a new PPPoS interface
 *
 * ppp_netif, netif to use for this PPP link, i.e. PPP IP interface
 * output_cb, PPPoS serial output callback
 * status_cb, PPP status callback, called on PPP status change (up, down, …)
 * ctx_cb, optional user-provided callback context pointer
 */
ppp = pppos_create(&ppp_netif,
       output_cb, status_cb, ctx_cb);
```

--------------------------------

### getpeername()

Source: https://www.nongnu.org/lwip/2_1_x/group__socket.html

Gets the remote address of a connected socket.

```APIDOC
## getpeername()

### Description
Gets the remote address of a connected socket.

### Function Signature
`getpeername(s, name, namelen)`

### Parameters
- **s** (int) - Required - Socket descriptor.
- **name** (struct sockaddr*) - Required - Buffer to store the remote address.
- **namelen** (socklen_t*) - Required - Pointer to the length of the address buffer.

### Returns
- **int** - 0 on success, or -1 on error.

### Notes
This is a macro that maps to `lwip_getpeername`.
```

--------------------------------

### Initiate PPP server listener

Source: https://www.nongnu.org/lwip/2_1_x/group__ppp.html

Configures a PPP server: sets local and peer IP addresses, DNS servers, authentication, requires peer authentication, and sets silent mode for PPPoS. Then initiates the listener. Must be called when the session is in the dead state.

```c
ip4_addr_t addr;

/* Set our address */
IP4_ADDR(&addr, 192,168,0,1);
ppp_set_ipcp_ouraddr(ppp, &addr);

/* Set peer(his) address */
IP4_ADDR(&addr, 192,168,0,2);
ppp_set_ipcp_hisaddr(ppp, &addr);

/* Set primary DNS server */
IP4_ADDR(&addr, 192,168,10,20);
ppp_set_ipcp_dnsaddr(ppp, 0, &addr);

/* Set secondary DNS server */
IP4_ADDR(&addr, 192,168,10,21);
ppp_set_ipcp_dnsaddr(ppp, 1, &addr);

/* Auth configuration, this is pretty self-explanatory */
ppp_set_auth(ppp, PPPAUTHTYPE_ANY, "login", "password");

/* Require peer to authenticate */
ppp_set_auth_required(ppp, 1);

/*
 * Only for PPPoS, the PPP session should be up and waiting for input.
 *
 * Note: for PPPoS, ppp_connect() and ppp_listen() are actually the same thing.
 * The listen call is meant for future support of PPPoE and PPPoL2TP server
 * mode, where we will need to negotiate the incoming PPPoE session or L2TP
 * session before initiating PPP itself. We need this call because there is
 * two passive modes for PPPoS, ppp_set_passive and ppp_set_silent.
 */
ppp_set_silent(pppos, 1);

/*
 * Initiate PPP listener (i.e. wait for an incoming connection), can only
 * be called if PPP session is in the dead state (i.e. disconnected).
 */
ppp_listen(ppp);
```

--------------------------------

### sntp_getoperatingmode

Source: https://www.nongnu.org/lwip/2_1_x/group__sntp.html

Gets the operating mode of the SNTP client.

```APIDOC
## sntp_getoperatingmode

### Description
Gets the operating mode of the SNTP client.

### Method
u8_t sntp_getoperatingmode(void)

### Parameters
None.

### Returns
u8_t - The operating mode.
```

--------------------------------

### sys_init

Source: https://www.nongnu.org/lwip/2_1_x/sys_8h.html

Initializes the system abstraction layer.

```APIDOC
## sys_init

### Description
Initializes the system abstraction layer.

### Function Signature
`void sys_init(void)`
```

--------------------------------

### sntp_enabled

Source: https://www.nongnu.org/lwip/2_1_x/group__sntp.html

Gets the enabled state of the SNTP client.

```APIDOC
## sntp_enabled

### Description
Gets the enabled state of the SNTP client.

### Method
u8_t sntp_enabled(void)

### Parameters
None.

### Returns
u8_t - Enabled state (non-zero if enabled).
```

--------------------------------

### altcp_listen macro

Source: https://www.nongnu.org/lwip/2_1_x/group__altcp.html

Macro to start listening on an altcp PCB with default backlog and no error callback.

```APIDOC
## altcp_listen macro

### Description
Macro to start listening on an altcp PCB with default backlog and no error callback. It expands to altcp_listen_with_backlog_and_err(conn, TCP_DEFAULT_LISTEN_BACKLOG, NULL).

### Method
Macro

### Definition
#define altcp_listen(conn) altcp_listen_with_backlog_and_err(conn, TCP_DEFAULT_LISTEN_BACKLOG, NULL)

### Parameters
- **conn** - The altcp PCB to listen on.

### See Also
altcp_listen_with_backlog_and_err
```

--------------------------------

### getsockopt

Source: https://www.nongnu.org/lwip/2_1_x/group__socket.html

Macro that maps to lwip_getsockopt for getting socket options.

```APIDOC
## getsockopt

### Description
Gets options for a socket.

### Macro Definition
#define getsockopt(s, level, optname, opval, optlen) lwip_getsockopt(s, level, optname, opval, optlen)

### Parameters
- **s** - Socket descriptor.
- **level** - Protocol level.
- **optname** - Option name.
- **opval** - Pointer to option value.
- **optlen** - Pointer to option length.

```

--------------------------------

### netconn_get_ipv6only(conn)

Source: https://www.nongnu.org/lwip/2_1_x/group__netconn__common.html

Macro to get the IPv6 only status of a netconn.

```APIDOC
## netconn_get_ipv6only(conn)

### Description
Gets the IPv6 only status of netconn calls (see NETCONN_FLAG_IPV6_V6ONLY).

### Macro Definition
#define netconn_get_ipv6only(conn) (((conn)->flags & NETCONN_FLAG_IPV6_V6ONLY) != 0)

### Parameters
- **conn** (struct netconn *) - Required - The netconn to query.

### Returns
Non-zero if IPv6 only is enabled, zero otherwise.
```

--------------------------------

### netif_set_up

Source: https://www.nongnu.org/lwip/2_1_x/group__netif.html

Marks a network interface as up, indicating it is ready to transmit and receive packets.

```APIDOC
## netif_set_up

### Description
Marks a network interface as up, indicating it is ready to transmit and receive packets.

### Function Signature
void netif_set_up (struct netif *netif)

### Parameters
- **netif** (struct netif *) - Required - Pointer to the netif to bring up.
```

--------------------------------

### netifapi_netif_set_up

Source: https://www.nongnu.org/lwip/2_1_x/group__netifapi__netif.html

Brings a network interface up. This macro is intended to be called from non-TCPIP threads.

```APIDOC
## netifapi_netif_set_up

### Description
Brings the network interface up (enables it). This macro is intended to be called from non-TCPIP threads.

### Macro Definition
```c
#define netifapi_netif_set_up(n) netifapi_netif_common(n, netif_set_up, NULL)
```

### Parameters
- **n** - Required - Pointer to the network interface.

### See Also
- netif_set_up()

```

--------------------------------

### ip_addr_get_ip4_u32

Source: https://www.nongnu.org/lwip/2_1_x/group__ip4addr.html

Gets the 32-bit IPv4 address value from an ip_addr_t.

```APIDOC
## ip_addr_get_ip4_u32

### Description
Gets the 32-bit IPv4 address value from an ip_addr_t.

### Macro Definition
#define ip_addr_get_ip4_u32(ipaddr)

### Parameters
- **ipaddr** (const ip_addr_t *) - Required - Pointer to the ip_addr_t to get the value from.

### Return Value
- **uint32_t** - The 32-bit IPv4 address in network byte order.

### Usage Example
```c
ip_addr_t addr = IPADDR4_INIT(0x01020304);
uint32_t val = ip_addr_get_ip4_u32(&addr);
```
```

--------------------------------

### netbuf_data()

Source: https://www.nongnu.org/lwip/2_1_x/globals_n.html

Gets data from a netbuf. Defined in netbuf.c and netbuf.h.

```APIDOC
## netbuf_data()

### Description
Gets data from a netbuf. This function is part of the lwIP netbuf API.

### Source
- netbuf.c
- netbuf.h

```

--------------------------------

### tftp_init

Source: https://www.nongnu.org/lwip/2_1_x/group__tftp.html

Initializes the TFTP server with the provided callback context. This function must be called before using the TFTP server.

```APIDOC
## tftp_init

### Description
Initializes the TFTP server with the provided callback context. This function must be called before using the TFTP server.

### Function Signature
`err_t tftp_init(const struct tftp_context *ctx)`

### Parameters
- **ctx** (const struct tftp_context *) - Required - TFTP callback struct

### Returns
- **err_t** - Error code indicating success or failure.

```

--------------------------------

### snmp_get_community_trap

Source: https://www.nongnu.org/lwip/2_1_x/apps_2snmp_8h.html

Gets the community string used for sending traps.

```APIDOC
## snmp_get_community_trap

### Description
Gets the community string used for sending traps.

### Method
const char *

### Signature
const char *snmp_get_community_trap(void)

### Parameters
None

### Returns
- **const char *** - Pointer to the trap community string.
```

--------------------------------

### mDNS responder overview and usage (configuration, API calls, example callback)

Source: https://www.nongnu.org/lwip/2_1_x/group__mdns.html

This block contains the main documentation for the lwIP mDNS responder. It includes configuration steps (LWIP_MDNS_RESPONDER, MDNS_MAX_SERVICES, MEMP_NUM_UDP_PCB, LWIP_NUM_NETIF_CLIENT_DATA, LWIP_IGMP, LWIP_AUTOIP, LWIP_IPV6_MLD), API function signatures (mdns_resp_init, mdns_resp_add_netif, mdns_resp_announce, mdns_resp_restart, mdns_resp_remove_netif, mdns_resp_add_service, mdns_resp_del_service), and an example TXT callback (srv_txt) that uses mdns_resp_add_service_txtitem. It also notes limitations, stack usage, and the need for a strncasecmp implementation.

```text
Multicast DNS for lwIP

Author: Erik Ekman


Note! The MDNS responder does not have all features required by the standards.
See notes in src/apps/mdns/mdns.c for what is left. It is however usable in normal
cases - but watch out if many devices on the same network try to use the same
host/service instance names.


How to enable:
==============

MDNS support does not depend on DNS.
MDNS supports using IPv4 only, v6 only, or v4+v6.

To enable MDNS responder, set
  LWIP_MDNS_RESPONDER = 1
in lwipopts.h and add src/apps/mdns/mdns.c to your list of files to build.

The max number of services supported per netif is defined by MDNS_MAX_SERVICES,
default is 1.

Increase MEMP_NUM_UDP_PCB by 1. MDNS needs one PCB.
Increase LWIP_NUM_NETIF_CLIENT_DATA by 1 (MDNS needs one entry on netif).

MDNS with IPv4 requires LWIP_IGMP = 1, and preferably LWIP_AUTOIP = 1.
MDNS with IPv6 requires LWIP_IPV6_MLD = 1, and that a link-local address is
generated.

The MDNS code puts its structs on the stack where suitable to reduce dynamic
memory allocation. It may use up to 1kB of stack.

MDNS (like other apps) needs a strncasecmp() implementation. If you have one, define
'lwip_strnicmp' to it. Otherwise the code will provide an implementation
for you.


How to use:
===========

Call mdns_resp_init() during system initialization.
This opens UDP sockets on port 5353 for IPv4 and IPv6.


To start responding on a netif, run
  mdns_resp_add_netif(struct netif *netif, char *hostname, u32_t dns_ttl)

The hostname will be copied. If this returns successfully, the netif will join
the multicast groups and any MDNS/legacy DNS requests sent unicast or multicast
to port 5353 will be handled:
- <hostname>.local type A, AAAA or ANY returns relevant IP addresses
- Reverse lookups (PTR in-addr.arpa, ip6.arpa) of netif addresses
  returns <hostname>.local
Answers will use the supplied TTL (in seconds)
MDNS allows UTF-8 names, but it is recommended to stay within ASCII,
since the default case-insensitive comparison assumes this.

Call mdns_resp_announce() every time the IP address on the netif has changed.

Call mdns_resp_restart() every time the network interface comes up after being
down, for example cable connected after being disconnected, administrative 
interface comes up after being down, or the device wakes up from sleep.

To stop responding on a netif, run
  mdns_resp_remove_netif(struct netif *netif)


Adding services:
================

The netif first needs to be registered. Then run
  mdns_resp_add_service(struct netif *netif, char *name, char *service,
      u16_t proto, u16_t port, u32_t dns_ttl,
      service_get_txt_fn_t txt_fn, void *txt_userdata);

The name and service pointers will be copied. Name refers to the name of the
service instance, and service is the type of service, like _http
proto can be DNSSD_PROTO_UDP or DNSSD_PROTO_TCP which represent _udp and _tcp.
If this call returns successfully, the following queries will be answered:
- _services._dns-sd._udp.local type PTR returns <service>.<proto>.local
- <service>.<proto>.local type PTR returns <name>.<service>.<proto>.local
- <name>.<service>.<proto>.local type SRV returns hostname and port of service
- <name>.<service>.<proto>.local type TXT builds text strings by calling txt_fn
  with the supplied userdata. The callback adds strings to the reply by calling
  mdns_resp_add_service_txtitem(struct mdns_service *service, char *txt,
   int txt_len). Example callback method:

   static void srv_txt(struct mdns_service *service, void *txt_userdata)
   {
     res = mdns_resp_add_service_txtitem(service, "path=/", 6);
     LWIP_ERROR("mdns add service txt failed\n", (res == ERR_OK), return);
   }

  Since a hostname struct is used for TXT storage each single item can be max
  63 bytes long, and  the total max length (including length bytes for each
  item) is 255 bytes.

If your device runs a webserver on port 80, an example call might be:

  mdns_resp_add_service(netif, "myweb", "_http"
      DNSSD_PROTO_TCP, 80, 3600, srv_txt, NULL);

which will publish myweb._http._tcp.local for any hosts looking for web servers,
and point them to <hostname>.local:80

Relevant information will be sent as additional records to reduce number of
requests required from a client.

To remove a service from a netif, run
  mdns_resp_del_service(struct netif *netif, s8_t slot)
```

--------------------------------

### snmp_get_auth_traps_enabled

Source: https://www.nongnu.org/lwip/2_1_x/apps_2snmp_8h.html

Gets whether authentication failure traps are enabled.

```APIDOC
## snmp_get_auth_traps_enabled

### Description
Gets whether authentication failure traps are enabled.

### Method
u8_t

### Signature
u8_t snmp_get_auth_traps_enabled(void)

### Parameters
None

### Returns
- **u8_t** - Non-zero if enabled, zero if disabled.
```

--------------------------------

### zepif_init

Source: https://www.nongnu.org/lwip/2_1_x/group__zepif.html

Initializes a ZEP netif, setting up a raw 6LowPAN netif and surrounding it with input and output functions for ZEP. This function is called when adding the netif via netif_add.

```APIDOC
## zepif_init

### Description
Set up a raw 6LowPAN netif and surround it with input- and output functions for ZEP.

### Function Signature
err_t zepif_init(struct netif *netif)

### Parameters
- **netif** (struct netif *) - Pointer to the netif structure to initialize.

### Return Value
- **err_t** - Error status indicating success or failure.

### Usage Example
```c
netif_add(&zep_netif, NULL, NULL, NULL, NULL, zepif_init, tcpip_6lowpan_input);
netif_create_ip6_linklocal_address(&zep_netif, 1);
netif_set_up(&zep_netif);
netif_set_link_up(&zep_netif);
```
```

--------------------------------

### SMTP send mail example with callback

Source: https://www.nongnu.org/lwip/2_1_x/group__smtp.html

Shows how to set the server address, authentication, and send an email with a result callback. The callback prints the results. Note: when using from any thread other than tcpip_thread (for NO_SYS==0), use smtp_send_mail_int() instead.

```c
void my_smtp_result_fn(void *arg, u8_t smtp_result, u16_t srv_err, err_t err)
{
printf("mail (%p) sent with results: 0x%02x, 0x%04x, 0x%08x\n", arg,
smtp_result, srv_err, err);
}
static void my_smtp_test(void)
{
smtp_set_server_addr("mymailserver.org");
-> set both username and password as NULL if no auth needed
smtp_set_auth("username", "password");
smtp_send_mail("sender", "recipient", "subject", "body", my_smtp_result_fn,
some_argument);
}
```

--------------------------------

### tcp_sndqueuelen

Source: https://www.nongnu.org/lwip/2_1_x/group__tcp__raw.html

Macro to get the length of the send queue of a TCP PCB.

```APIDOC
## tcp_sndqueuelen

### Description
Macro to get the length of the send queue of a TCP PCB.

### Macro Definition
#define tcp_sndqueuelen(pcb) ((pcb)->snd_queuelen)

### Parameters
- **pcb** (struct tcp_pcb *) - Required - The TCP PCB.

### Return Value
- **u16_t** - The send queue length.

```

--------------------------------

### netbiosns_init()

Source: https://www.nongnu.org/lwip/2_1_x/globals_n.html

Initializes the NetBIOS name service. Defined in netbiosns.c and netbiosns.h.

```APIDOC
## netbiosns_init()

### Description
Initializes the NetBIOS name service. This function is part of the lwIP NetBIOS name service module.

### Source
- netbiosns.c
- netbiosns.h

```

--------------------------------

### netbuf_first()

Source: https://www.nongnu.org/lwip/2_1_x/globals_n.html

Gets the first pbuf in a netbuf. Defined in netbuf.c and netbuf.h.

```APIDOC
## netbuf_first()

### Description
Gets the first pbuf in a netbuf. This function is part of the lwIP netbuf API.

### Source
- netbuf.c
- netbuf.h

```

--------------------------------

### nd6_get_destination_mtu()

Source: https://www.nongnu.org/lwip/2_1_x/globals_n.html

Gets the destination MTU for IPv6. Defined in nd6.c and nd6.h.

```APIDOC
## nd6_get_destination_mtu()

### Description
Gets the MTU (Maximum Transmission Unit) for a destination in IPv6 Neighbor Discovery. This function is part of the lwIP ND6 module.

### Source
- nd6.c
- nd6.h

```

--------------------------------

### lwiperf_start_tcp_server()

Source: https://www.nongnu.org/lwip/2_1_x/group__iperf.html

Starts a TCP iperf server on a specified IP address and port, listening for incoming connections from iperf clients.

```APIDOC
## lwiperf_start_tcp_server()

### Description
Starts a TCP iperf server on a specific IP address and port, listening for incoming connections from iperf clients.

### Function Signature
```c
void* lwiperf_start_tcp_server(const ip_addr_t* _local_addr_, u16_t _local_port_, lwiperf_report_fn _report_fn_, void* _report_arg_)
```

### Parameters
- **local_addr** (const ip_addr_t*) - Required - The local IP address to bind the server to.
- **local_port** (u16_t) - Required - The local port to listen on.
- **report_fn** (lwiperf_report_fn) - Required - Callback function for reporting results.
- **report_arg** (void*) - Required - User argument passed to the report callback.

### Returns
- **void*** - A connection handle that can be used to abort the server by calling lwiperf_abort().
```

--------------------------------

### mem_init()

Source: https://www.nongnu.org/lwip/2_1_x/mem_8c.html

Initializes the dynamic memory manager.

```APIDOC
## mem_init()

### Description
Initializes the dynamic memory manager.

### Method
Function

### Signature
void mem_init(void)

### Parameters
None

### Returns
void
```
Tokens:
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