libstore: allow specifying port for ssh[-ng] stores

This also adds documentation for it in distributed-builds.md as that's
possibly the most common use-case for remote ssh stores

Support for `std::optional<uint16_t>` in Setting is also added since
setting a port is optional.

The line `#include "lix/libutil/strings.hh"` fixes that templates instanciations
in lix/libutil/config-impl.hh were using string utils without including
the header (why are they even there btw)

Change-Id: Id806c117c48cdf158d9d1cb1e639b0df31d9bf11

doc/manual/change-authors.yml

@@ -153,6 +153,9 @@ roberth:
   display_name: Robert Hensing
   github: roberth
 
+seppel3210:
+  github: Seppel3210
+
 teofilc:
   forgejo: teofilc
   github: TeofilC

doc/manual/rl-next/ssh-store-port.md

@@ -0,0 +1,10 @@
+---
+synopsis: 'Allow specifying ports for remote ssh[-ng] stores'
+issues: []
+cls: [2432]
+category: Improvements
+credits: [seppel3210]
+---
+
+You can now specify which port should be used for a remote ssh store (e.g. for remote/distributed builds) through a uri parameter.
+E.g., when a remote builder `foo` is listening on port `1234` instead of the default, it can be specified like this `ssh://foo?port=1234`.

doc/manual/src/advanced-topics/distributed-builds.md

@@ -75,7 +75,9 @@ by spaces. Only the first element is required. To leave a field at its
 default, set it to `-`.
 
 1.  The URI of the remote store in the format
-    `ssh://[username@]hostname`, e.g. `ssh://nix@mac` or `ssh://mac`.
+    `ssh://[username@]hostname[?port=<port>]`, e.g. `ssh://nix@mac` or `ssh://mac`.
+    If the ssh server is not listening on port 22 (e.g. port 1337 in this case)
+    the URI would be `ssh://nix@mac?port=1337`
     For backward compatibility, `ssh://` may be omitted. The hostname
     may be an alias defined in your `~/.ssh/config`.
 

lix/libstore/legacy-ssh-store.cc

@@ -12,6 +12,8 @@
 #include "lix/libutil/result.hh"
 #include "lix/libutil/strings.hh"
 #include "lix/libstore/derivations.hh"
+#include "lix/libutil/config-impl.hh"
+#include "lix/libutil/abstract-setting-to-json.hh"
 
 namespace nix {
 
@@ -113,6 +115,7 @@ struct LegacySSHStore final : public Store
             ))
         , master(
             host,
+            config_.port,
             config_.sshKey,
             config_.sshPublicHostKey,
             // Use SSH master only if using more than 1 connection.

lix/libstore/legacy-ssh-store.md

@@ -1,6 +1,6 @@
 R"(
 
-**Store URL format**: `ssh://[username@]hostname`
+**Store URL format**: `ssh://[username@]hostname[?port=42069]`
 
 This store type allows limited access to a remote store on another
 machine via SSH.

lix/libstore/ssh-store.cc

@@ -39,6 +39,7 @@ public:
         , host(host)
         , master(
             host,
+            config_.port,
             config_.sshKey,
             config_.sshPublicHostKey,
             // Use SSH master only if using more than 1 connection.

lix/libstore/ssh-store.hh

@@ -2,6 +2,7 @@
 ///@file
 
 #include "lix/libstore/store-api.hh"
+#include <cstdint>
 
 namespace nix {
 
@@ -9,6 +10,9 @@ struct CommonSSHStoreConfig : virtual StoreConfig
 {
     using StoreConfig::StoreConfig;
 
+    const Setting<std::optional<uint16_t>> port{this, std::nullopt, "port",
+        "Port that should be used instead of the default on the remote machine."};
+
     const Setting<Path> sshKey{this, "", "ssh-key",
         "Path to the SSH private key used to authenticate to the remote machine."};
 

lix/libstore/ssh-store.md

@@ -1,6 +1,6 @@
 R"(
 
-**Store URL format**: `ssh-ng://[username@]hostname`
+**Store URL format**: `ssh-ng://[username@]hostname[?port=42069]`
 
 Experimental store type that allows full access to a Nix store on a
 remote machine.

lix/libstore/ssh.cc

@@ -8,8 +8,9 @@
 
 namespace nix {
 
-SSHMaster::SSHMaster(const std::string & host, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD)
+SSHMaster::SSHMaster(const std::string & host, const std::optional<uint16_t> port, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD)
     : host(host)
+    , port(port)
     , fakeSSH(host == "localhost")
     , keyFile(keyFile)
     , sshPublicHostKey(sshPublicHostKey)
@@ -28,6 +29,8 @@ void SSHMaster::addCommonSSHOpts(Strings & args)
 {
     auto state(state_.lock());
 
+    if (port.has_value())
+        args.insert(args.end(), {"-p", std::to_string(*port)});
     for (auto & i : tokenizeString<Strings>(getEnv("NIX_SSHOPTS").value_or("")))
         args.push_back(i);
     if (!keyFile.empty())

lix/libstore/ssh.hh

@@ -4,6 +4,7 @@
 #include "lix/libutil/file-system.hh"
 #include "lix/libutil/processes.hh"
 #include "lix/libutil/sync.hh"
+#include <cstdint>
 
 namespace nix {
 
@@ -12,6 +13,7 @@ class SSHMaster
 private:
 
     const std::string host;
+    const std::optional<uint16_t> port;
     bool fakeSSH;
     const std::string keyFile;
     const std::string sshPublicHostKey;
@@ -33,7 +35,7 @@ private:
 
 public:
 
-    SSHMaster(const std::string & host, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD = -1);
+    SSHMaster(const std::string & host, const std::optional<uint16_t> port, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD = -1);
 
     struct Connection
     {

lix/libutil/config-impl.hh

@@ -15,6 +15,7 @@
 #include "lix/libutil/args.hh"
 #include "lix/libutil/config.hh"
 #include "lix/libutil/logging.hh"
+#include "lix/libutil/strings.hh"
 
 namespace nix {
 
@@ -123,6 +124,7 @@ void BaseSetting<T>::convertToArg(Args & args, const std::string & category)
 
 DECLARE_CONFIG_SERIALISER(std::string)
 DECLARE_CONFIG_SERIALISER(std::optional<std::string>)
+DECLARE_CONFIG_SERIALISER(std::optional<uint16_t>)
 DECLARE_CONFIG_SERIALISER(bool)
 DECLARE_CONFIG_SERIALISER(Strings)
 DECLARE_CONFIG_SERIALISER(StringSet)

lix/libutil/config.cc

@@ -270,6 +270,21 @@ template<> std::string BaseSetting<std::optional<std::string>>::to_string() cons
     return value ? *value : "";
 }
 
+template<> std::optional<uint16_t> BaseSetting<std::optional<uint16_t>>::parse(const std::string & str, const ApplyConfigOptions & options) const
+{
+    if (str == "")
+        return std::nullopt;
+    else if (auto n = string2Int<uint16_t>(str))
+        return n;
+    else
+        throw UsageError("setting '%s' has invalid value '%s'", name, str);
+}
+
+template<> std::string BaseSetting<std::optional<uint16_t>>::to_string() const
+{
+    return value ? std::to_string(*value) : "";
+}
+
 template<> bool BaseSetting<bool>::parse(const std::string & str, const ApplyConfigOptions & options) const
 {
     if (str == "true" || str == "yes" || str == "1")