wasmbuild

Documentation

Overview

Package wasmbuild contains the shared build flags and manifest layout used to produce the @tailscale/connect NPM package's main.wasm. It is imported both by cmd/tsconnect (which does the build) and by tests that verify the produced pkg/main.wasm matches what the current source tree would build (see tstest/integration/jswasmtest).

Index

• Constants
• Variables
• func ProdCommand(goBin, outputPath string) *exec.Cmd
• func Tags() string
• type BuildInfo

Constants

const BuildInfoFile = "build-info.json"

BuildInfoFile is the basename of the JSON manifest that build-pkg writes alongside main.wasm, recording the sha256 of the raw (pre-wasm-opt) go-build output. Tests use this to detect a stale pkg/main.wasm without having to re-run wasm-opt themselves.

const ProdLDFlags = "-s -w"

ProdLDFlags is the -ldflags value used in production wasm builds. -s strips the symbol table, -w strips DWARF, both to shrink the shipped artifact.

Variables

var Keep = []featuretags.FeatureTag{
	"c2n",
	"dns",
	"health",
	"ipnbus",
	"logtail",
	"netstack",
}

Keep is the set of feature/featuretags tags the cmd/tsconnect/wasm build needs LINKED. Every other feature in featuretags.Features is excluded via its ts_omit_ build tag (computed by Tags). Transitive dependencies of entries in Keep are pulled in automatically via featuretags.Requires.

Adding an entry here grows the wasm bundle. Removing one strips it. The init() below panics if any entry is unknown to feature/featuretags, so a rename / removal in that registry fails loudly here.

Notably absent (server-only or otherwise meaningless in a browser):

• "ssh": controls the SSH *server* (feature/ssh registers ssh/tailssh). The wasm acts as an SSH *client* using golang.org/x/crypto/ssh directly; no featuretag gates that.
• "portmapper", "debugportmapper": js/wasm has no UDP sockets, can't speak NAT-PMP / PCP / UPnP.
• "captiveportal": the browser handles captive portal detection in front of us.
• "syspolicy": no MDM in a browser.
• "drive", "taildrop", "peerapi*": no local filesystem.
• "clientupdate": no binary self-update.
• "dbus", "resolved", "networkmanager", "iptables", "linkspeed", "linuxdnsfight", "listenrawdisco", "osrouter", "synology", "systray", "tundevstats", "wakeonlan": OS integrations not applicable to a browser-hosted client.
• "aws", "cloud", "kube", "bird", "appconnectors", "conn25", "relayserver", "serve", "acme", "tap", "tpm", "doctor", "advertiseroutes", "advertiseexitnode", "useroutes", "useexitnode": server-side or otherwise out of scope for the SSH-in-browser / fetch-in-browser use case.

Functions

func ProdCommand

func ProdCommand(goBin, outputPath string) *exec.Cmd

ProdCommand returns an *exec.Cmd that runs `go build` for cmd/tsconnect/wasm with the production flags, writing the raw (pre-wasm-opt) wasm to outputPath. GOOS=js GOARCH=wasm is set in the command's environment. The caller is responsible for wiring Stdin/Stdout/Stderr and invoking Run.

If goBin is empty, runtime.GOROOT()+"/bin/go" is used so that the build runs under the same toolchain that built the caller.

func Tags

func Tags() string

Tags returns the joined -tags value for the wasm build: [baseTags] plus a ts_omit_<feature> for every entry in featuretags.Features that is not transitively required by Keep.

The result is sorted so that the same source tree always produces the same string (and therefore the same wasm bytes, given identical inputs to `go build`).

Types

type BuildInfo

type BuildInfo struct {
	// RawWasmSHA256 is the lowercase hex sha256 of the wasm bytes as
	// they came out of `go build` (before wasm-opt was run in place).
	RawWasmSHA256 string `json:"raw_wasm_sha256"`
}

BuildInfo is the JSON contents of BuildInfoFile.