platform: modularize api/gui, add docs-tests-web foundation, and refresh root config

selective-vpn-api/app/transport_netns_spec.go

@@ -0,0 +1,127 @@
+package app
+
+import (
+	"fmt"
+	"hash/fnv"
+	"net/netip"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func transportBuildNetnsSpec(client TransportClient) (transportNetnsSpec, error) {
+	ns := transportNetnsName(client)
+	if ns == "" {
+		return transportNetnsSpec{}, fmt.Errorf("netns name is empty")
+	}
+	pfx, err := transportNetnsPrefix(client)
+	if err != nil {
+		return transportNetnsSpec{}, err
+	}
+	hostIP := pfx.Addr().Next()
+	peerIP := hostIP.Next()
+	if !hostIP.IsValid() || !peerIP.IsValid() || !pfx.Contains(peerIP) {
+		return transportNetnsSpec{}, fmt.Errorf("netns subnet has no usable host pair: %s", pfx.String())
+	}
+
+	uplink := strings.TrimSpace(transportConfigString(client.Config, "netns_uplink_iface"))
+	if uplink == "" {
+		mainRoute, err := transportDetectMainIPv4Route()
+		if err != nil {
+			return transportNetnsSpec{}, err
+		}
+		uplink = strings.TrimSpace(mainRoute.Dev)
+	}
+	if uplink == "" {
+		return transportNetnsSpec{}, fmt.Errorf("netns uplink iface is empty")
+	}
+
+	tag := transportShortHash("netns:"+ns, 8)
+	return transportNetnsSpec{
+		Name:     ns,
+		HostVeth: "svh" + tag,
+		PeerVeth: "svn" + tag,
+		Prefix:   pfx,
+		HostIP:   hostIP,
+		PeerIP:   peerIP,
+		Uplink:   uplink,
+	}, nil
+}
+
+func transportNetnsName(client TransportClient) string {
+	raw := strings.TrimSpace(transportConfigString(client.Config, "netns_name"))
+	if raw == "" {
+		base := sanitizeID(client.ID)
+		if base == "" {
+			base = "client"
+		}
+		raw = "svpn-" + base
+	}
+	return normalizeTransportNetnsName(raw, client.ID)
+}
+
+func normalizeTransportNetnsName(raw, fallbackClientID string) string {
+	ns := sanitizeID(raw)
+	if ns == "" {
+		base := sanitizeID(fallbackClientID)
+		if base == "" {
+			base = "client"
+		}
+		ns = "svpn-" + base
+	}
+	if len(ns) > 63 {
+		ns = ns[:63]
+	}
+	return ns
+}
+
+func transportNetnsPrefix(client TransportClient) (netip.Prefix, error) {
+	raw := strings.TrimSpace(transportConfigString(client.Config, "netns_subnet"))
+	if raw == "" {
+		seed := transportShortHash(client.ID, 2)
+		n, _ := strconv.ParseUint(seed, 16, 8)
+		raw = fmt.Sprintf("10.240.%d.0/30", 10+int(n)%200)
+	}
+	pfx, err := netip.ParsePrefix(raw)
+	if err != nil {
+		return netip.Prefix{}, fmt.Errorf("invalid netns_subnet: %q", raw)
+	}
+	pfx = pfx.Masked()
+	if !pfx.Addr().Is4() {
+		return netip.Prefix{}, fmt.Errorf("netns_subnet must be IPv4: %q", raw)
+	}
+	if pfx.Bits() > 30 {
+		return netip.Prefix{}, fmt.Errorf("netns_subnet must provide at least 2 host addresses: %q", raw)
+	}
+	return pfx, nil
+}
+
+func transportNetnsExists(name string) (bool, error) {
+	stdout, stderr, code, err := transportRunCommand(4*time.Second, "ip", "netns", "list")
+	if err != nil || code != 0 {
+		return false, transportCommandError("ip netns list", stdout, stderr, code, err)
+	}
+	for _, line := range strings.Split(stdout, "\n") {
+		fields := strings.Fields(strings.TrimSpace(line))
+		if len(fields) == 0 {
+			continue
+		}
+		if fields[0] == name {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+func transportShortHash(raw string, n int) string {
+	if n <= 0 {
+		n = 8
+	}
+	h := fnv.New32a()
+	_, _ = h.Write([]byte(strings.TrimSpace(raw)))
+	s := fmt.Sprintf("%08x", h.Sum32())
+	if n >= len(s) {
+		return s
+	}
+	return s[:n]
+}