From 27e0133d40f7b328482b501a18e22b12a55564ea Mon Sep 17 00:00:00 2001
From: Star Rauchenberger <fefferburbia@gmail.com>
Date: Sun, 13 Jul 2025 10:07:59 -0400
Subject: Associate

---
 src/retransmit.c | 169 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 169 insertions(+)
 create mode 100644 src/retransmit.c

(limited to 'src/retransmit.c')

diff --git a/src/retransmit.c b/src/retransmit.c
new file mode 100644
index 0000000..44f609c
--- /dev/null
+++ b/src/retransmit.c
@@ -0,0 +1,169 @@
+#include "retransmit.h"
+
+#include <libwifi.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "transmit.h"
+
+static pthread_mutex_t retransmitter_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+void ack_map_init(struct ack_map *map)
+{
+  map->top = NULL;
+}
+
+void ack_map_add(struct ack_map *map, const unsigned char dst_addr[6], const unsigned char *packet, int packet_size)
+{
+  struct ack_map_node *cur = map->top;
+  struct ack_map_node *prev = NULL;
+
+  while (cur != NULL)
+  {
+    prev = cur;
+    cur = cur->next;
+  }
+
+  struct ack_map_node *next = (struct ack_map_node *)malloc(sizeof(struct ack_map_node));
+  next->next = NULL;
+  memcpy(next->dst_addr, dst_addr, 6);
+  next->packet = (unsigned char *)malloc(packet_size);
+  memcpy(next->packet, packet, packet_size);
+  next->packet_size = packet_size;
+  next->retries_left = 7;
+
+  if (prev == NULL)
+  {
+    map->top = next;
+  }
+  else
+  {
+    prev->next = next;
+  }
+}
+
+void ack_map_pop(struct ack_map *map)
+{
+  if (map->top != NULL)
+  {
+    struct ack_map_node *cur = map->top;
+    map->top = cur->next;
+
+    free(cur->packet);
+    free(cur);
+  }
+}
+
+int ack_map_length(struct ack_map *map)
+{
+  int result = 0;
+
+  struct ack_map_node *cur = map->top;
+  while (cur != NULL)
+  {
+    result++;
+
+    cur = cur->next;
+  }
+
+  return result;
+}
+
+void ack_map_clear(struct ack_map *map)
+{
+  while (map->top != NULL)
+  {
+    ack_map_pop(map);
+  }
+}
+
+void *retransmit_thread(void *arg)
+{
+  struct retransmitter *retransmitter = (struct retransmitter *)arg;
+
+  for (;;)
+  {
+    pthread_mutex_lock(&retransmitter_mutex);
+
+    if (retransmitter->quit)
+    {
+      pthread_mutex_unlock(&retransmitter_mutex);
+
+      break;
+    }
+
+    struct ack_map_node *cur = retransmitter->messages.top;
+    if (cur != NULL)
+    {
+      send_packet_with_radiotap(retransmitter->sock, retransmitter->device_index, cur->dst_addr, cur->packet, cur->packet_size);
+
+      // Set retransmit flag for future.
+      cur->packet[1] |= (1 << 3);
+
+      cur->retries_left--;
+
+      if (cur->retries_left <= 0)
+      {
+        ack_map_pop(&retransmitter->messages);
+      }
+    }
+
+    pthread_mutex_unlock(&retransmitter_mutex);
+
+    usleep(5000);
+  }
+
+  return NULL;
+}
+
+struct retransmitter *start_retransmit_thread(int sock, int device_index)
+{
+  struct retransmitter *retransmitter = (struct retransmitter *)malloc(sizeof(struct retransmitter));
+  retransmitter->sock = sock;
+  retransmitter->device_index = device_index;
+  ack_map_init(&retransmitter->messages);
+  retransmitter->quit = false;
+
+  pthread_create(&retransmitter->thread_id, NULL, &retransmit_thread, retransmitter);
+
+  return retransmitter;
+}
+
+void send_until_acked(struct retransmitter *retransmitter, const unsigned char dst_addr[6], const unsigned char *packet, int packet_size)
+{
+  pthread_mutex_lock(&retransmitter_mutex);
+
+  ack_map_add(&retransmitter->messages, dst_addr, packet, packet_size);
+
+  printf("Adding message for " MACSTR ". Current length: %d\n", MAC2STR(dst_addr), ack_map_length(&retransmitter->messages));
+
+  pthread_mutex_unlock(&retransmitter_mutex);
+}
+
+void handle_ack(struct retransmitter *retransmitter)
+{
+  pthread_mutex_lock(&retransmitter_mutex);
+
+  if (retransmitter->messages.top != NULL)
+  {
+    retransmitter->messages.top->retries_left = 0;
+  }
+
+  printf("Received ACK. Current length: %d\n", ack_map_length(&retransmitter->messages));
+
+  pthread_mutex_unlock(&retransmitter_mutex);
+}
+
+void free_retransmitter(struct retransmitter *retransmitter)
+{
+  pthread_mutex_lock(&retransmitter_mutex);
+  retransmitter->quit = true;
+  pthread_mutex_unlock(&retransmitter_mutex);
+
+  pthread_join(retransmitter->thread_id, NULL);
+
+  ack_map_clear(&retransmitter->messages);
+  free(retransmitter);
+}
-- 
cgit 1.4.1