From 5b06f1735822ebc1f0cc046051df6df80b1e21c2 Mon Sep 17 00:00:00 2001
From: AlexSSD7 <alexandersadovskyi7@protonmail.com>
Date: Thu, 31 Aug 2023 16:17:46 +0100
Subject: [PATCH] Net tap alloc storage

---
 storage/nettap.go | 91 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 storage/nettap.go

diff --git a/storage/nettap.go b/storage/nettap.go
new file mode 100644
index 0000000..663ce51
--- /dev/null
+++ b/storage/nettap.go
@@ -0,0 +1,91 @@
+package storage
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"github.com/AlexSSD7/linsk/nettap"
+	"github.com/pkg/errors"
+)
+
+const tapAllocPrefix = "tap_alloc_"
+
+func (s *Storage) getAllocFilePath(tapName string) (string, error) {
+	err := nettap.ValidateTapName(tapName)
+	if err != nil {
+		return "", errors.Wrap(err, "validate tap name")
+	}
+
+	return filepath.Join(s.path, tapAllocPrefix+tapName), nil
+}
+
+func (s *Storage) SaveNetTapAllocation(tapName string, pid int) error {
+	allocFilePath, err := s.getAllocFilePath(tapName)
+	if err != nil {
+		return errors.Wrap(err, "get alloc file path")
+	}
+
+	err = os.WriteFile(allocFilePath, []byte(fmt.Sprint(pid)), 0400)
+	if err != nil {
+		return errors.Wrap(err, "write alloc file")
+	}
+
+	return nil
+}
+
+func (s *Storage) ReleaseNetTapAllocation(tapName string) error {
+	allocFilePath, err := s.getAllocFilePath(tapName)
+	if err != nil {
+		return errors.Wrap(err, "get alloc file path")
+	}
+
+	// TODO: Check what happens the file doesn't exist. It should not return an error.
+	err = os.Remove(allocFilePath)
+	if err != nil {
+		return errors.Wrap(err, "remove alloc file")
+	}
+
+	return nil
+}
+
+func (s *Storage) ListNetTapAllocations() ([]nettap.NetTapAlloc, error) {
+	dirEntries, err := os.ReadDir(s.path)
+	if err != nil {
+		return nil, errors.Wrap(err, "read data dir")
+	}
+
+	var ret []nettap.NetTapAlloc
+
+	for _, entry := range dirEntries {
+		if strings.HasPrefix(entry.Name(), tapAllocPrefix) {
+			entryPath := filepath.Join(s.path, entry.Name())
+
+			tapName := strings.TrimPrefix(entry.Name(), tapAllocPrefix)
+			err := nettap.ValidateTapName(tapName)
+			if err != nil {
+				s.logger.Error("Failed to validate network tap name in tap allocation file, skipping. External interference?", "error", err.Error(), "name", tapName, "path", entryPath)
+				continue
+			}
+
+			data, err := os.ReadFile(entryPath)
+			if err != nil {
+				return nil, errors.Wrapf(err, "read tap alloc file '%v'", entryPath)
+			}
+
+			pid, err := strconv.ParseUint(string(data), 10, strconv.IntSize-1) // We're aiming for `int` PID.
+			if err != nil {
+				return nil, errors.Wrapf(err, "parse pid (alloc file '%v')", entryPath)
+			}
+
+			ret = append(ret, nettap.NetTapAlloc{
+				TapName: tapName,
+				PID:     int(pid),
+			})
+		}
+	}
+
+	return ret, nil
+}