new-app: configure jail mail relay and persist the jail's network alias

Two provisioning gaps in new-app:

- The jail's dma.conf inherited the base image's shared SMARTHOST/
  PORT/AUTHPATH, but never got a per-app MAILNAME - without one, dma
  can misroute mail for recipients on the jail's own apex domain as
  local delivery. EnableMail appends a MAILNAME of <app>.skiff.local,
  which can't collide with any real domain an app sends to or from.

- A classic jail's ip4.addr is only a bind restriction, not a route,
  until something aliases it onto a host interface. jail.conf.tmpl
  never set jail(8)'s own `interface` parameter, so nothing ever
  created that alias - confirmed on skiff-freebsd, where the address
  had twice been made to work via an ad hoc `ifconfig alias` that
  didn't survive a reboot. Setting `interface` lets jail(8) manage
  the alias itself, including on every boot.

1 files changed, 5 insertions, 1 deletions

diff --git a/cmd/skiff/main.go b/cmd/skiff/main.go
index 7c9d505..8ca1406 100644
--- a/cmd/skiff/main.go
+++ b/cmd/skiff/main.go
@@ -84,6 +84,7 @@ func cmdNewApp(args []string) error {
 	healthPath := fs.String("health-path", layout.DefaultHealthPath, "health check path")
 	serverName := fs.String("server-name", "", "nginx server_name (defaults to <name>)")
 	baseSnapshot := fs.String("base-snapshot", "ready", "snapshot on the base dataset to clone from")
+	iface := fs.String("iface", layout.DefaultJailIface, "host interface the jail's IP is aliased onto")
 	fs.Parse(args)
 
 	if *name == "" || *ip == "" {
@@ -115,9 +116,12 @@ func cmdNewApp(args []string) error {
 		return fmt.Errorf("initialize env file: %w", err)
 	}
 
-	if err := jailmgr.WriteConf(cfg, *name, *ip); err != nil {
+	if err := jailmgr.WriteConf(cfg, *name, *ip, *iface); err != nil {
 		return fmt.Errorf("write jail config: %w", err)
 	}
+	if err := jailmgr.EnableMail(cfg, *name); err != nil {
+		return fmt.Errorf("configure mail: %w", err)
+	}
 
 	if err := appmeta.Write(cfg.MetaPath(*name), appmeta.Meta{
 		IP:         *ip,