ipv6 abbreviated address support

Help output:

```
$> ./et --help
Remote shell for the busy and impatient
Usage:
  et [OPTION...] [user@]host[:port]

  Note that 'host' can be a hostname or ipv4 address with or without a port
  or an ipv6 address. If the ipv6 address is abbreviated with :: then it must
  be specfied without a port (use -p,--port).

  -h, --help                 Print help
      --version              Print version
  -u, --username             Username
      --host arg             Remote host name
  ...
```
Tests:

```
$> ./et ::1 -p 8080 --macserver
$> ./et 0:0:0:0:0:0:0:1 -p 8080 --macserver
$> ./et 0:0:0:0:0:0:0:1:8080 --macserver
$> ./et ::1 -p 8080 --macserver # fails because defaults to port 2022
```
Fixes #537

.circleci/config.yml

@@ -38,6 +38,12 @@ jobs:
  - run:
  name: Connect new -> old (ipv6 with port in host)
  command: build/et -c "ls" 0:0:0:0:0:0:0:1:2022 --logtostdout --verbose=9
+ - run:
+ name: Connect new -> old (ipv6 abbreviated)
+ command: build/et -c "ls" ::1 --logtostdout --verbose=9
+ - run:
+ name: Connect new -> old (ipv6 abbreviated with port arg)
+ command: build/et -c "ls" ::1 --port 2022 --logtostdout --verbose=9
  - run:
  name: Kill server
  command: sudo pkill etserver

src/terminal/TerminalClientMain.cpp

@@ -38,60 +38,65 @@ int main(int argc, char** argv) {
  // Parse command line arguments
  cxxopts::Options options("et", "Remote shell for the busy and impatient");
  try {
- options.positional_help("[user@]hostname[:port]").show_positional_help();
  options.allow_unrecognised_options();
-
- options.add_options() //
- ("h,help", "Print help") //
- ("version", "Print version") //
- ("u,username", "Username") //
+ options.positional_help("");
+ options.custom_help("[OPTION...] [user@]host[:port]\n\n"
+ " Note that 'host' can be a hostname or ipv4 address with or without a port\n"
+ " or an ipv6 address. If the ipv6 address is abbreviated with :: then it must\n"
+ " be specfied without a port (use -p,--port)."
+ );
+
+ options.add_options()
+ ("h,help", "Print help")
+ ("version", "Print version")
+ ("u,username", "Username")
  ("host", "Remote host name",
- cxxopts::value<std::string>()) //
- ("p,port", "Remote machine port",
- cxxopts::value<int>()->default_value("2022")) //
+ cxxopts::value<std::string>())
+ ("p,port", "Remote machine etserver port",
+ cxxopts::value<int>()->default_value("2022"))
  ("c,command", "Run command on connect",
- cxxopts::value<std::string>()) //
+ cxxopts::value<std::string>())
  ("terminal-path", "Path to etterminal on server side. "
  "Use if etterminal is not on the system path.",
- cxxopts::value<std::string>()) //
+ cxxopts::value<std::string>())
  ("t,tunnel",
  "Tunnel: Array of source:destination ports or "
  "srcStart-srcEnd:dstStart-dstEnd (inclusive) port ranges (e.g. "
  "10080:80,10443:443, 10090-10092:8000-8002)",
- cxxopts::value<std::string>()) //
+ cxxopts::value<std::string>())
  ("r,reversetunnel",
  "Reverse Tunnel: Array of source:destination ports or "
  "srcStart-srcEnd:dstStart-dstEnd (inclusive) port ranges",
- cxxopts::value<std::string>()) //
+ cxxopts::value<std::string>())
  ("jumphost", "jumphost between localhost and destination",
- cxxopts::value<std::string>()) //
+ cxxopts::value<std::string>())
  ("jport", "Jumphost machine port",
- cxxopts::value<int>()->default_value("2022")) //
+ cxxopts::value<int>()->default_value("2022"))
  ("x,kill-other-sessions",
- "kill all old sessions belonging to the user") //
+ "kill all old sessions belonging to the user")
  ("macserver",
  "Set when connecting to an macOS server. Sets "
- "--terminal-path=/usr/local/bin/etterminal") //
+ "--terminal-path=/usr/local/bin/etterminal")
  ("v,verbose", "Enable verbose logging",
- cxxopts::value<int>()->default_value("0")) //
+ cxxopts::value<int>()->default_value("0"))
  ("k,keepalive", "Client keepalive duration in seconds",
- cxxopts::value<int>()) //
- ("logtostdout", "Write log to stdout") //
- ("silent", "Disable logging") //
- ("N,no-terminal", "Do not create a terminal") //
- ("f,forward-ssh-agent", "Forward ssh-agent socket") //
+ cxxopts::value<int>())
+ ("logtostdout", "Write log to stdout")
+ ("silent", "Disable logging")
+ ("N,no-terminal", "Do not create a terminal")
+ ("f,forward-ssh-agent", "Forward ssh-agent socket")
  ("ssh-socket", "The ssh-agent socket to forward",
- cxxopts::value<std::string>()) //
+ cxxopts::value<std::string>())
  ("telemetry",
  "Allow et to anonymously send errors to guide future improvements",
- cxxopts::value<bool>()->default_value("true")) //
+ cxxopts::value<bool>()->default_value("true"))
  ("serverfifo",
- "If set, communicate to etserver on the matching fifo name", //
- cxxopts::value<std::string>()->default_value("")) //
+ "If set, communicate to etserver on the matching fifo name",
+ cxxopts::value<std::string>()->default_value(""))
  ("ssh-option", "Options to pass down to `ssh -o`",
  cxxopts::value<std::vector<std::string>>());
 
- options.parse_positional({"host", "positional"});
+ options.parse_positional({"host"});
 
  auto result = options.parse(argc, argv);
  if (result.count("help")) {
@@ -154,24 +159,43 @@ int main(int argc, char** argv) {
 
  if (host_arg.find(':') != string::npos) {
  int colon_count = std::count(host_arg.begin(), host_arg.end(), ':');
- if (colon_count == 1 || colon_count == 8) {
- // ipv4 or hostname or ipv6 with port specified
+ if (colon_count == 1) {
+ // ipv4 or hostname with port specified
  int port_colon_pos = host_arg.rfind(':');
  destinationPort = stoi(host_arg.substr(port_colon_pos + 1));
  host_arg = host_arg.substr(0, port_colon_pos);
- } else if (colon_count == 7) {
- // ipv6 without port specified
  } else {
- CLOG(INFO, "stdout") << "Invalid host positional arg: "
- << result["host"].as<std::string>() << endl;
- exit(1);
+ // maybe ipv6 (colon_count >= 2)
+ if(host_arg.find("::") != string::npos) {
+ // ipv6 with double colon zero abbreviation and no port
+ // leave host_arg as is
+ } else {
+ if (colon_count == 7) {
+ // ipv6, fully expanded, without port
+ } else if (colon_count == 8) {
+ // ipv6, fully expanded, with port
+ int port_colon_pos = host_arg.rfind(':');
+ destinationPort = stoi(host_arg.substr(port_colon_pos + 1));
+ host_arg = host_arg.substr(0, port_colon_pos);
+ } else {
+ CLOG(INFO, "stdout") << "Invalid host positional arg: "
+ << result["host"].as<std::string>() << endl;
+ exit(1);
+ }
+ }
  }
+ // CLOG(INFO, "stdout") << "Invalid host positional arg: "
+ // << result["host"].as<std::string>() << endl;
+ // exit(1);
  }
  destinationHost = host_arg;
+ // host_alias is used for the initiating ssh call, if sshd runs on a port
+ // other than 22, either configure your .ssh/config with an alias with an
+ // overridden port or pass --ssh-option Port=<sshd_port>
+ string host_alias = destinationHost;
 
  string jumphost =
  result.count("jumphost") ? result["jumphost"].as<string>() : "";
- string host_alias = destinationHost;
  int keepaliveDuration = result.count("keepalive") ? result["keepalive"].as<int>() : MAX_CLIENT_KEEP_ALIVE_DURATION;
  if (keepaliveDuration < 1 || keepaliveDuration > MAX_CLIENT_KEEP_ALIVE_DURATION) {
  CLOG(INFO, "stdout") << "Keep-alive duration must between 1 and " << MAX_CLIENT_KEEP_ALIVE_DURATION << " seconds" << endl;