ipn/ipnlocal: add c2n /debug/pprof/allocs endpoint

This behaves the same as typical debug/pprof/allocs.

Updates tailscale/corp#18514

Signed-off-by: Percy Wegmann <percy@tailscale.com>

ipn/ipnlocal/c2n_pprof.go

@@ -6,6 +6,7 @@
 package ipnlocal
 
 import (
+	"fmt"
 	"net/http"
 	"runtime"
 	"runtime/pprof"
@@ -20,4 +21,25 @@ func init() {
 		}
 		pprof.WriteHeapProfile(w)
 	}
+
+	c2nPprof = func(w http.ResponseWriter, r *http.Request, profile string) {
+		w.Header().Set("X-Content-Type-Options", "nosniff")
+		p := pprof.Lookup(string(profile))
+		if p == nil {
+			http.Error(w, "Unknown profile", http.StatusNotFound)
+			return
+		}
+		gc, _ := strconv.Atoi(r.FormValue("gc"))
+		if profile == "heap" && gc > 0 {
+			runtime.GC()
+		}
+		debug, _ := strconv.Atoi(r.FormValue("debug"))
+		if debug != 0 {
+			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		} else {
+			w.Header().Set("Content-Type", "application/octet-stream")
+			w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, profile))
+		}
+		p.WriteTo(w, debug)
+	}
 }