feat: Add debugging setup for vscode

Dockerfile.debug

@@ -0,0 +1,37 @@
+FROM --platform=${BUILDPLATFORM} mcr.microsoft.com/oss/go/microsoft/golang:1.22@sha256:9e5243001d0f43d6e1c556a0ce8eedc1bc80eb37b5210036b289d2c601bc08b6 AS go
+FROM scratch AS dlv-ctx
+
+FROM go  AS frontend-build
+ARG HOSTDIR
+WORKDIR ${HOSTDIR}
+COPY . .
+ENV CGO_ENABLED=0
+ARG TARGETARCH TARGETOS GOFLAGS=-trimpath
+ENV GOOS=${TARGETOS} GOARCH=${TARGETARCH} GOFLAGS=${GOFLAGS}
+RUN \
+    --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    go build -tags=debug -gcflags="all=-N -l" -o /frontend ./cmd/frontend && \
+    go build -o /dalec-redirectio ./cmd/dalec-redirectio
+
+FROM go AS dlv-build
+ARG HOSTDIR
+WORKDIR /dlv
+ADD https://github.com/go-delve/delve.git#v1.23.1 .
+ENV CGO_ENABLED=0
+ARG TARGETARCH TARGETOS GOFLAGS=-trimpath
+ENV GOOS=${TARGETOS} GOARCH=${TARGETARCH} GOFLAGS=${GOFLAGS}
+RUN \
+    --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    make build
+
+FROM mcr.microsoft.com/azurelinux/distroless/base:3.0 AS frontend
+ARG HOSTDIR
+COPY . ${HOSTDIR}
+COPY --from=frontend-build /frontend /frontend
+COPY --from=frontend-build /dalec-redirectio /dalec-redirectio
+COPY --from=dlv-build /dlv/dlv /usr/local/bin/dlv
+LABEL moby.buildkit.frontend.network.none="true"
+LABEL moby.buildkit.frontend.caps="moby.buildkit.frontend.inputs,moby.buildkit.frontend.subrequests,moby.buildkit.frontend.contexts"
+ENTRYPOINT ["/frontend"]

cmd/frontend/debug.go

@@ -0,0 +1,64 @@
+//go:build debug
+
+package main
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+	"syscall"
+)
+
+func waitForDebug(ctx context.Context) error {
+	pid := fmt.Sprintf("%d", syscall.Getpid())
+	cmd := exec.Command(
+		"dlv",
+		"attach",
+		"--api-version=2",
+		"--headless",
+		"--listen=unix:/dlv.sock",
+		"--allow-non-terminal-interactive",
+		pid,
+	)
+	cmd.Stdout = io.Discard
+	cmd.Stderr = io.Discard
+
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	go func() {
+		if err := cmd.Wait(); err != nil {
+			panic(err)
+		}
+	}()
+
+	tracerPid := "0"
+	for tracerPid == "0" {
+		b, err := os.Open("/proc/self/status")
+		if err != nil {
+			return err
+		}
+
+		s := bufio.NewScanner(b)
+		for s.Scan() {
+			start, end, ok := strings.Cut(s.Text(), ":\t")
+			if !ok {
+				continue
+			}
+
+			if start != "TracerPid" {
+				continue
+			}
+
+			tracerPid = end
+			break
+		}
+	}
+
+	return nil
+}

cmd/frontend/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	_ "embed"
 	"os"
 
@@ -10,6 +11,7 @@ import (
 	"github.com/Azure/dalec/frontend/debug"
 	"github.com/Azure/dalec/frontend/ubuntu"
 	"github.com/Azure/dalec/frontend/windows"
+	gwclient "github.com/moby/buildkit/frontend/gateway/client"
 	"github.com/moby/buildkit/frontend/gateway/grpcclient"
 	"github.com/moby/buildkit/util/appcontext"
 	"github.com/moby/buildkit/util/bklog"
@@ -31,16 +33,27 @@ func main() {
 
 	mux.Add(debug.DebugRoute, debug.Handle, nil)
 
-	if err := grpcclient.RunFromEnvironment(ctx, mux.Handler(
-		// copy/paster's beware: [frontend.WithTargetForwardingHandler] should not be set except for the root dalec frontend.
-		frontend.WithBuiltinHandler(azlinux.Mariner2TargetKey, azlinux.NewMariner2Handler()),
-		frontend.WithBuiltinHandler(azlinux.AzLinux3TargetKey, azlinux.NewAzlinux3Handler()),
-		frontend.WithBuiltinHandler(windows.DefaultTargetKey, windows.Handle),
-		ubuntu.Handlers,
-		debian.Handlers,
-		frontend.WithTargetForwardingHandler,
-	)); err != nil {
+	f := func(ctx context.Context, client gwclient.Client) (*gwclient.Result, error) {
+		if err := waitForDebug(ctx); err != nil {
+			return nil, err
+		}
+
+		handlerFunc := mux.Handler(
+			// copy/paster's beware: [frontend.WithTargetForwardingHandler] should not be set except for the root dalec frontend.
+			frontend.WithBuiltinHandler(azlinux.Mariner2TargetKey, azlinux.NewMariner2Handler()),
+			frontend.WithBuiltinHandler(azlinux.AzLinux3TargetKey, azlinux.NewAzlinux3Handler()),
+			frontend.WithBuiltinHandler(windows.DefaultTargetKey, windows.Handle),
+			ubuntu.Handlers,
+			debian.Handlers,
+			frontend.WithTargetForwardingHandler,
+		)
+
+		return handlerFunc(ctx, client)
+	}
+
+	if err := grpcclient.RunFromEnvironment(ctx, f); err != nil {
 		bklog.L.WithError(err).Fatal("error running frontend")
 		os.Exit(137)
 	}
+
 }

cmd/frontend/no_debug.go

@@ -0,0 +1,9 @@
+//go:build !debug
+
+package main
+
+import "context"
+
+func waitForDebug(ctx context.Context) error {
+	return nil
+}

debug/debug.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -eux
+
+if [ -z "$(command -v socat)" ]; then
+    echo you must have "'socat'" installed
+    exit 1
+fi
+
+if [ -z "$(command -v pgrep)" ]; then
+    echo you must have "'pgrep'" installed
+    exit 1
+fi
+
+PROJECT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "${PROJECT_DIR}"
+
+# Build frontend with debugging setup Note the host path for the dalec source
+# and the in-container build path must be the same
+REF="local/dalec/frontend:tmp"
+docker build \
+    -f Dockerfile.debug \
+    -t "${REF}" \
+    --build-arg=HOSTDIR="${PROJECT_DIR}" \
+    .
+
+# Wait for frontend process to start, and forward the socket connection when the process has started
+(
+    set +x
+    pid=""
+    while [ -z "$pid" ]; do
+        sleep 0.5
+        pid="$(pgrep frontend)"
+    done
+    set -x
+
+    socat_logfile="$(mktemp)"
+    socat -v UNIX:"/proc/${pid}/root/dlv.sock" TCP-LISTEN:30157,reuseaddr,fork 2>"$socat_logfile"
+    socat_pid="$!"
+    trap "kill -9 ${socat_pid}" EXIT
+) &
+
+# Run the build
+exec docker build --build-arg=BUILDKIT_SYNTAX="${REF}" "$@"