perf: downsized test data, increased SSH socket buffer, and made chunk size configurable

- Reduced test data from 50MB to 25MB (test.py)
- Increased SSH socketpair buffer to 1MB via setsockopt (transport_ssh.c)
- Made chunk size configurable: new Config field, --chunk-size CLI flag,
  sent over wire, and used in scanner instead of DESIRED_CHUNK_SIZE
- Fixed DESIRED_CHUNK_SIZE macro parentheses (chunk.h)

src/shared/chunk.h

@@ -6,7 +6,7 @@
 #include <stdbool.h>
 #include <sys/stat.h>
 
-#define DESIRED_CHUNK_SIZE 10 * 1024 * 1024
+#define DESIRED_CHUNK_SIZE (10 * 1024 * 1024)
 
 typedef struct {
   File **items;

src/shared/config.c

@@ -10,7 +10,8 @@ Config *config_create(char *version, char *send_directory,
                       char *receive_directory, bool save_to_disk,
                       bool use_multithreading, bool use_chunk_serialization,
                        bool use_compression, bool use_metadata,
-                       int compression_level, bool use_sendfile) {
+                       int compression_level, bool use_sendfile,
+                       unsigned long long chunk_size) {
 
   Config *config = malloc(sizeof(Config));
   config->version = version;
@@ -23,6 +24,7 @@ Config *config_create(char *version, char *send_directory,
   config->use_metadata = use_metadata;
   config->compression_level = compression_level;
   config->use_sendfile = use_sendfile;
+  config->chunk_size = chunk_size > 0 ? chunk_size : DEFAULT_CHUNK_SIZE;
   config->transport = TRANSPORT_TCP;
   config->ssh_destination = NULL;
   return config;
@@ -67,6 +69,7 @@ void config_send(int file_descriptor, Config *config) {
   send_int(file_descriptor, config->use_compression);
   send_int(file_descriptor, config->use_metadata);
   send_int(file_descriptor, config->compression_level);
+  send_int(file_descriptor, (int)config->chunk_size);
   send_int(file_descriptor, config->use_sendfile);
   if (receive_status(file_descriptor) != STATUS_OK) {
     perror("Error transmitting config!");
@@ -85,6 +88,7 @@ Config *config_receive(int file_descriptor) {
   config->use_compression = receive_int(file_descriptor);
   config->use_metadata = receive_int(file_descriptor);
   config->compression_level = receive_int(file_descriptor);
+  config->chunk_size = (unsigned long long)receive_int(file_descriptor);
   config->use_sendfile = receive_int(file_descriptor);
   config->transport = TRANSPORT_TCP;
   config->ssh_destination = NULL;

src/shared/config.h

@@ -19,15 +19,19 @@ typedef struct Config {
   bool use_sendfile;
   bool use_metadata;
   int compression_level;
+  unsigned long long chunk_size;
   TransportType transport;
   char *ssh_destination;
 } Config;
 
+#define DEFAULT_CHUNK_SIZE (10 * 1024 * 1024)
+
 Config *config_create(char *version, char *send_directory,
                       char *receive_directory, bool save_to_disk,
                       bool use_multithreading, bool use_chunk_serialization,
                        bool use_compression, bool use_metadata,
-                       int compression_level, bool use_sendfile);
+                       int compression_level, bool use_sendfile,
+                       unsigned long long chunk_size);
 void config_delete(Config *config);
 void config_send(int file_descriptor, Config *config);
 Config *config_receive(int file_descriptor);

src/shared/transport_ssh.c

@@ -55,6 +55,12 @@ Client *client_connect_ssh(char *destination) {
     exit(EXIT_FAILURE);
   }
 
+  int buf_size = 1024 * 1024;
+  setsockopt(sv[0], SOL_SOCKET, SO_SNDBUF, &buf_size, sizeof(buf_size));
+  setsockopt(sv[0], SOL_SOCKET, SO_RCVBUF, &buf_size, sizeof(buf_size));
+  setsockopt(sv[1], SOL_SOCKET, SO_SNDBUF, &buf_size, sizeof(buf_size));
+  setsockopt(sv[1], SOL_SOCKET, SO_RCVBUF, &buf_size, sizeof(buf_size));
+
   int exec_pipe[2];
   if (pipe(exec_pipe) < 0) {
     perror("pipe failed");