feat: add basic proxy

.gitignore

@@ -0,0 +1,9 @@
+# Devenv
+.devenv*
+devenv.local.nix
+
+# direnv
+.direnv
+
+# pre-commit
+.pre-commit-config.yaml

devenv.lock

@@ -0,0 +1,103 @@
+{
+  "nodes": {
+    "devenv": {
+      "locked": {
+        "dir": "src/modules",
+        "lastModified": 1747185494,
+        "owner": "cachix",
+        "repo": "devenv",
+        "rev": "b292bc94c2daccda165bc9f909bf6c8056e37a80",
+        "type": "github"
+      },
+      "original": {
+        "dir": "src/modules",
+        "owner": "cachix",
+        "repo": "devenv",
+        "type": "github"
+      }
+    },
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1747046372,
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "9100a0f413b0c601e0533d1d94ffd501ce2e7885",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "git-hooks": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "gitignore": "gitignore",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1746537231,
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "rev": "fa466640195d38ec97cf0493d6d6882bc4d14969",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "type": "github"
+      }
+    },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "git-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1709087332,
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "637db329424fd7e46cf4185293b9cc8c88c95394",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1746807397,
+        "owner": "cachix",
+        "repo": "devenv-nixpkgs",
+        "rev": "c5208b594838ea8e6cca5997fbf784b7cca1ca90",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "ref": "rolling",
+        "repo": "devenv-nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "devenv": "devenv",
+        "git-hooks": "git-hooks",
+        "nixpkgs": "nixpkgs",
+        "pre-commit-hooks": [
+          "git-hooks"
+        ]
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

devenv.nix

@@ -0,0 +1,7 @@
+{ pkgs, lib, config, inputs, ... }:
+
+{
+  packages = [ pkgs.git ];
+
+  languages.go.enable = true;
+}

devenv.yaml

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+# yaml-language-server: $schema=https://devenv.sh/devenv.schema.json
+inputs:
+  nixpkgs:
+    url: github:cachix/devenv-nixpkgs/rolling
+
+# If you're using non-OSS software, you can set allowUnfree to true.
+# allowUnfree: true
+
+# If you're willing to use a package that's vulnerable
+# permittedInsecurePackages:
+#  - "openssl-1.1.1w"
+
+# If you have more than one devenv you can merge them
+#imports:
+# - ./backend

go.mod

@@ -0,0 +1,3 @@
+module git.yadunut.dev/yadunut/tcp_proxy
+
+go 1.24.2

main.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"context"
+	"io"
+	"log"
+	"net"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+	"time"
+)
+
+func getEnv(key string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	log.Fatalf("env %s must be set", key)
+	return ""
+}
+
+func main() {
+	listenAddr := getEnv("LISTEN_ADDR")
+	upstreamAddr := getEnv("UPSTREAM_ADDR")
+
+	listener, err := net.Listen("tcp", listenAddr)
+	if err != nil {
+		log.Fatalf("listen: %v", err)
+	}
+	log.Printf("proxy listening on %s, forwarding to %s", listenAddr, upstreamAddr)
+
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+
+	go func() {
+		<-ctx.Done()
+		log.Println("closing proxy")
+		listener.Close()
+	}()
+
+	var wg sync.WaitGroup
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			if ctx.Err() != nil {
+				log.Println("Listen context error")
+				break
+			}
+			log.Printf("accept: %v", err)
+			continue
+		}
+
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			handleConn(ctx, conn, upstreamAddr)
+		}()
+	}
+	wg.Wait()
+}
+
+func handleConn(ctx context.Context, client net.Conn, upstreamAddr string) {
+	defer client.Close()
+
+	upstream, err := net.DialTimeout("tcp", upstreamAddr, 5*time.Second)
+	if err != nil {
+		log.Printf("dial upstream: %v", err)
+		return
+	}
+	defer upstream.Close()
+
+	var wg sync.WaitGroup
+
+	wg.Add(2)
+	go copyAndClose(&wg, client, upstream)
+	go copyAndClose(&wg, upstream, client)
+	wg.Wait()
+}
+
+func copyAndClose(wg *sync.WaitGroup, dst, src net.Conn) {
+	defer wg.Done()
+	defer dst.Close()
+	_, err := io.Copy(dst, src)
+	if err != nil {
+		log.Printf("copy %v", err)
+	}
+}