[security] transport.Controller{} and transport.Transport{} security and performance improvements (#564)

* cache transports in controller by privkey-generated pubkey, add retry logic to transport requests

Signed-off-by: kim <grufwub@gmail.com>

* update code comments, defer mutex unlocks

Signed-off-by: kim <grufwub@gmail.com>

* add count to 'performing request' log message

Signed-off-by: kim <grufwub@gmail.com>

* reduce repeated conversions of same url.URL object

Signed-off-by: kim <grufwub@gmail.com>

* move worker.Worker to concurrency subpackage, add WorkQueue type, limit transport http client use by WorkQueue

Signed-off-by: kim <grufwub@gmail.com>

* fix security advisories regarding max outgoing conns, max rsp body size

- implemented by a new httpclient.Client{} that wraps an underlying
  client with a queue to limit connections, and limit reader wrapping
  a response body with a configured maximum size
- update pub.HttpClient args passed around to be this new httpclient.Client{}

Signed-off-by: kim <grufwub@gmail.com>

* add httpclient tests, move ip validation to separate package + change mechanism

Signed-off-by: kim <grufwub@gmail.com>

* fix merge conflicts

Signed-off-by: kim <grufwub@gmail.com>

* use singular mutex in transport rather than separate signer mus

Signed-off-by: kim <grufwub@gmail.com>

* improved useragent string

Signed-off-by: kim <grufwub@gmail.com>

* add note regarding missing test

Signed-off-by: kim <grufwub@gmail.com>

* remove useragent field from transport (instead store in controller)

Signed-off-by: kim <grufwub@gmail.com>

* shutup linter

Signed-off-by: kim <grufwub@gmail.com>

* reset other signing headers on each loop iteration

Signed-off-by: kim <grufwub@gmail.com>

* respect request ctx during retry-backoff sleep period

Signed-off-by: kim <grufwub@gmail.com>

* use external pkg with docs explaining performance "hack"

Signed-off-by: kim <grufwub@gmail.com>

* use http package constants instead of string method literals

Signed-off-by: kim <grufwub@gmail.com>

* add license file headers

Signed-off-by: kim <grufwub@gmail.com>

* update code comment to match new func names

Signed-off-by: kim <grufwub@gmail.com>

* updates to user-agent string

Signed-off-by: kim <grufwub@gmail.com>

* update signed testrig models to fit with new transport logic (instead uses separate signer now)

Signed-off-by: kim <grufwub@gmail.com>

* fuck you linter

Signed-off-by: kim <grufwub@gmail.com>

internal/concurrency/workers.go

@@ -0,0 +1,104 @@
+package concurrency
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"path"
+	"reflect"
+	"runtime"
+
+	"codeberg.org/gruf/go-runners"
+	"github.com/sirupsen/logrus"
+)
+
+// WorkerPool represents a proccessor for MsgType objects, using a worker pool to allocate resources.
+type WorkerPool[MsgType any] struct {
+	workers runners.WorkerPool
+	process func(context.Context, MsgType) error
+	prefix  string // contains type prefix for logging
+}
+
+// New returns a new WorkerPool[MsgType] with given number of workers and queue ratio,
+// where the queue ratio is multiplied by no. workers to get queue size. If args < 1
+// then suitable defaults are determined from the runtime's GOMAXPROCS variable.
+func NewWorkerPool[MsgType any](workers int, queueRatio int) *WorkerPool[MsgType] {
+	var zero MsgType
+
+	if workers < 1 {
+		// ensure sensible workers
+		workers = runtime.GOMAXPROCS(0)
+	}
+	if queueRatio < 1 {
+		// ensure sensible ratio
+		queueRatio = 100
+	}
+
+	// Calculate the short type string for the msg type
+	msgType := reflect.TypeOf(zero).String()
+	_, msgType = path.Split(msgType)
+
+	w := &WorkerPool[MsgType]{
+		workers: runners.NewWorkerPool(workers, workers*queueRatio),
+		process: nil,
+		prefix:  fmt.Sprintf("worker.Worker[%s]", msgType),
+	}
+
+	// Log new worker creation with type prefix
+	logrus.Infof("%s created with workers=%d queue=%d",
+		w.prefix,
+		workers,
+		workers*queueRatio,
+	)
+
+	return w
+}
+
+// Start will attempt to start the underlying worker pool, or return error.
+func (w *WorkerPool[MsgType]) Start() error {
+	logrus.Infof("%s starting", w.prefix)
+
+	// Check processor was set
+	if w.process == nil {
+		return errors.New("nil Worker.process function")
+	}
+
+	// Attempt to start pool
+	if !w.workers.Start() {
+		return errors.New("failed to start Worker pool")
+	}
+
+	return nil
+}
+
+// Stop will attempt to stop the underlying worker pool, or return error.
+func (w *WorkerPool[MsgType]) Stop() error {
+	logrus.Infof("%s stopping", w.prefix)
+
+	// Attempt to stop pool
+	if !w.workers.Stop() {
+		return errors.New("failed to stop Worker pool")
+	}
+
+	return nil
+}
+
+// SetProcessor will set the Worker's processor function, which is called for each queued message.
+func (w *WorkerPool[MsgType]) SetProcessor(fn func(context.Context, MsgType) error) {
+	if w.process != nil {
+		logrus.Panicf("%s Worker.process is already set", w.prefix)
+	}
+	w.process = fn
+}
+
+// Queue will queue provided message to be processed with there's a free worker.
+func (w *WorkerPool[MsgType]) Queue(msg MsgType) {
+	logrus.Tracef("%s queueing message (workers=%d queue=%d): %+v",
+		w.prefix, w.workers.Workers(), w.workers.Queue(), msg,
+	)
+	w.workers.Enqueue(func(ctx context.Context) {
+		if err := w.process(ctx, msg); err != nil {
+			logrus.Errorf("%s %v", w.prefix, err)
+		}
+	})
+}