client: Exponential backoff resend intervals

[tattlekey] / client / net.c

#include "net.h"
#include "blink.h"
#include "config.h"

#include "pico/cyw43_arch.h"

#include "lwip/pbuf.h"
#include "lwip/udp.h"

/* We only ever send to one address, and we only ever have one thread, so just
 * use one udp_pcb */
static struct udp_pcb *the_pcb = NULL;

static void initialize_the_pcb() {
  if (the_pcb)
    return;

  the_pcb = udp_new();
  if (!the_pcb)
    signal_error_by_blinking();

  ip_addr_t ipaddr;
  if (ip4addr_aton(config_tattle_server_ip_address, &ipaddr) == 0)
    signal_error_by_blinking();

  if (udp_connect(the_pcb, &ipaddr, config_tattle_port) != ERR_OK)
    signal_error_by_blinking();
}

struct tattle_message_wire_format {
  u16_t sender;
  u16_t seq;
  u16_t ago;
};

void send_report(u16_t seq, u16_t ago) {
  cyw43_arch_lwip_begin();

  initialize_the_pcb();

  struct pbuf *p = pbuf_alloc(
      PBUF_TRANSPORT, sizeof(struct tattle_message_wire_format), PBUF_RAM);
  if (!p)
    signal_error_by_blinking();

  struct tattle_message_wire_format *msg =
      (struct tattle_message_wire_format *)(p->payload);
  msg->sender = htons(config_this_tattler_identity);
  msg->seq = htons(seq);
  msg->ago = htons(ago);

  if (udp_send(the_pcb, p) != ERR_OK)
    signal_error_by_blinking();

  pbuf_free(p);

  cyw43_arch_lwip_end();
}