update airdrop protocol (#153)

* update airdrop protocol

* fix lint

include/airdrop/packet.h

@@ -4,7 +4,7 @@
 #include <stdint.h>
 
 /**********************************************************************************************
- * LAST UPDATED: 2024/02/29
+ * LAST UPDATED: 2024/04/15 by Tyler Lentz
  * 
  * This file defines the packet definitions for Airdrop communications. It is used in two
  * separate repositories: 
@@ -27,18 +27,23 @@
 #define AD_OBC_PORT     45906  // OBC listens on this port, so payloads send to this
 #define AD_PAYLOAD_PORT 45907  // Payloads listen on this port, so OBC sends to this
 
-// All of the values in here are 1 byte long, which means we do not have to worry about
-// the endianness of the information as it is sent over the wire. If we ever add values more
-// than one byte long, we'll have to worry about this.
-
-// gcc specific packing syntax. Technically this should already be packed because it is just
-// two one-byte values, but just making sure.
+// Normal packet, which applies for every kind of packet that is not an ad_latlng_packet
 struct __attribute__((packed)) ad_packet {
     uint8_t hdr;
     uint8_t data;
 };
 typedef struct ad_packet ad_packet_t;
 
+// Separate kind of packet sent by OBC to Payloads to specify drop location
+// for indirect drop
+struct __attribute__((packed)) ad_latlng_packet {
+    uint8_t hdr;
+    uint8_t bottle;
+    double lat;
+    double lng;
+};
+typedef struct ad_latlng_packet ad_latlng_packet_t;
+
 enum ad_packet_hdr {
     // Continually sent by the payloads to confirm they are still operational
     // and can talk to the OBC
@@ -56,6 +61,8 @@ enum ad_packet_hdr {
     ACK_SIGNAL  = 201,
     REVOKE      = 202,
     ACK_REVOKE  = 203,
+    SEND_LATLNG = 204,  // special packet format!
+    ACK_LATLNG  = 205,
 
     // Direct & Indirect
     ABOUT_TO_RELEASE = 255,

include/network/airdrop_client.hpp

@@ -24,6 +24,7 @@ class AirdropClient {
     ~AirdropClient();
 
     bool send(ad_packet_t packet);
+    bool send(ad_latlng_packet_t packet);
     // Receives oldest packet since last receive() call, ignoring any
     // HEARTBEAT packets as those are parsed by the client itself
     // and exposed through the TODO function.

include/network/airdrop_sockets.h

@@ -67,6 +67,7 @@ ad_int_result_t set_socket_nonblocking(int sock_fd);
 // Either returns an error string or the number of bytes sent.
 // IMPORTANT: must have previously called set_send_thread from curr thread.
 ad_int_result_t send_ad_packet(ad_socket_t socket, ad_packet_t packet);
+ad_int_result_t send_ad_latlng_packet(ad_socket_t socket, ad_latlng_packet_t packet);
 
 // Receive packet and place into buf, which is of length buf_len.
 // Either returns an error string or the number of bytes read.

src/network/airdrop_client.cpp

@@ -72,6 +72,20 @@ bool AirdropClient::send(ad_packet_t packet) {
     return true;
 }
 
+bool AirdropClient::send(ad_latlng_packet_t packet) {
+    set_send_thread();
+
+    auto res = send_ad_latlng_packet(this->socket, packet);
+    if (res.is_err) {
+        LOG_F(ERROR, "%s", res.data.err);
+        return false;
+    }
+
+    // TODO: helper to go from packet -> str
+    LOG_F(INFO, "Sent airdrop latlng packet: %hhu %hhu", packet.hdr, packet.bottle);
+    return true;
+}
+
 std::optional<ad_packet_t> AirdropClient::receive() {
     Lock lock(this->recv_mut);
 

src/network/airdrop_sockets.c

@@ -118,6 +118,26 @@ ad_int_result_t send_ad_packet(ad_socket_t socket, ad_packet_t packet) {
     AD_RETURN_SUCC_RESULT(int, bytes_sent);
 }
 
+ad_int_result_t send_ad_latlng_packet(ad_socket_t socket, ad_latlng_packet_t packet) {
+    struct sockaddr_in SEND_ADDR = {
+        .sin_family = AF_INET,
+        .sin_port = htons(socket.send_port),
+        .sin_addr = INADDR_BROADCAST,
+        .sin_zero = {0},
+    };
+
+    static char err[AD_ERR_LEN];
+    int bytes_sent = sendto(socket.fd, (void*) &packet, sizeof(ad_latlng_packet_t), 0,
+                            (struct sockaddr*) &SEND_ADDR, sizeof(SEND_ADDR));
+
+    if (bytes_sent < 0) {
+        snprintf(&err[0], AD_ERR_LEN, "send failed: %s", strerror_l(errno, _send_locale));
+        AD_RETURN_ERR_RESULT(int, err);
+    }
+
+    AD_RETURN_SUCC_RESULT(int, bytes_sent);
+}
+
 ad_int_result_t recv_ad_packet(ad_socket_t socket, void* buf, size_t buf_len) {
     static char err[AD_ERR_LEN];
     struct sockaddr_in RECV_ADDR = {

src/network/mock/airdrop_sockets.c

@@ -70,6 +70,11 @@ ad_int_result_t send_ad_packet(ad_socket_t socket, ad_packet_t packet) {
     AD_RETURN_SUCC_RESULT(int, sizeof(ad_packet_t));
 }
 
+ad_int_result_t send_ad_latlng_packet(ad_socket_t socket, ad_latlng_packet_t packet) {
+    // TODO: Mock sending ad_latlng_packets
+    fprintf(stderr, "ERR: haven't yet implemented sending ad latlng packets in mock");
+}
+
 ad_int_result_t recv_ad_packet(ad_socket_t socket, void* buf, size_t buf_len) {
     static char err[1] = "";