Tidy up pxe flow

serving/dnsmasq/entrypoint.sh

@@ -23,8 +23,12 @@
 set -eu
 
 mkdir -p /srv/tftp
-# User-supplied iPXE binary (ipxe.efi) from the read-only source mount.
+# User-supplied iPXE binary (snponly.efi) from the read-only source mount.
 cp -f /tftp-src/*.efi /srv/tftp/ 2>/dev/null || true
+# autoexec.ipxe was an STP-era workaround (ifopen+retry before autoboot); it's no
+# longer rendered — PortFast on the switch port is the real fix. Remove any stale
+# copy left in a long-lived container's writable layer.
+rm -f /srv/tftp/autoexec.ipxe
 
 extract_cmdline() {  # $1 = UKI path; echoes the cleaned cmdline (empty on failure)
   uki="$1"
@@ -47,49 +51,28 @@ render_boot_ipxe() {
     echo "      hit a dracut shell under Secure Boot OFF (no embedded cmdline)." >&2
     echo "      Check the /artifacts mount + binutils, or enable Secure Boot." >&2
   fi
-  # Render the SAME boot logic to two files:
-  #   autoexec.ipxe — iPXE fetches + runs this at STARTUP (before autoboot). The
-  #     leading `ifopen net0` brings the link UP on NICs whose NII/UNDI link iPXE
-  #     can't establish during autoboot — e.g. EliteBook 820 G4 / Intel I219-LM,
-  #     which sits at link:down ("No configurable methods") until ifopen. Without
-  #     this, autoboot fails before it can even DHCP for boot.ipxe.
-  #   boot.ipxe — the DHCP-bootfile fallback (tag:ipxe) for firmware that DOES
-  #     autoboot-DHCP fine; harmless to carry the same ifopen.
-  # Both feed iPXE the UKI's REAL cmdline via imgargs (Secure Boot OFF; see top).
-  for f in /srv/tftp/autoexec.ipxe /srv/tftp/boot.ipxe; do
-    cat > "$f" <<EOF
+  # boot.ipxe is fetched as the DHCP bootfile (dnsmasq tag:ipxe) AFTER iPXE's
+  # normal autoboot DHCP has already configured the link, so it just fetches and
+  # boots the UKI. `imgargs` feeds the UKI's REAL cmdline (Secure Boot OFF — see
+  # top); without it iPXE would pass the image name as the cmdline and dracut
+  # would drop to an emergency shell. (every fallible step is '||'-guarded — a
+  # bare failure aborts the iPXE script.)
+  #
+  # REQUIRES PortFast/edge on the switch port: iPXE's autoboot opens the NIC,
+  # which bounces the PHY; without PortFast the switch's STP forwarding delay
+  # (~30s) drops the DHCP and the boot fails. (We removed the old ifopen+retry
+  # workaround now that PortFast is the documented requirement — serving/tftp/README.)
+  cat > /srv/tftp/boot.ipxe <<EOF
 #!ipxe
-# NOTE: in iPXE a bare failing command aborts the script (-> iPXE exits -> the
-# firmware restarts PXE), so EVERY step that can fail is guarded with '||'.
-#
-# The link is already up + forwarding here (the TFTP fetch of this script just
-# succeeded), so try DHCP FIRST without touching the PHY — on a PortFast/edge
-# port this succeeds immediately with no delay.
-dhcp net0 && goto have_ip || echo initial DHCP failed; will reset link and retry
-# Fallback: reset the link, then retry DHCP long enough to outlast the switch's
-# STP forwarding delay (~30s) that the ifopen bounce triggers. A single ifopen
-# (held open across the loop) means the PHY bounces ONCE; STP then converges and
-# a later DHCP gets through. PROPER fix is PortFast/edge on the switch port so
-# there's no delay at all — see serving/tftp/README.md.
-ifopen net0 || goto err
-set tries 0
-:dhcp_retry
-dhcp net0 && goto have_ip || echo DHCP retry \${tries}
-inc tries || goto err
-iseq \${tries} 30 && goto no_ip || sleep 3
-goto dhcp_retry
-:have_ip
+dhcp net0 || goto err
 imgfetch http://${SERVER_IP}/${uki} || goto err
 imgargs ${uki} ${cmdline}
 boot ${uki} || goto err
-:no_ip
-echo No DHCP after ~90s on net0 - enable PortFast/edge on the switch port (STP delay).
 :err
 echo Fleet iPXE chain failed (\${errno}) - dropping to iPXE shell
 shell
 EOF
-  done
-  echo "rendered autoexec.ipxe + boot.ipxe -> ${uki} (cmdline: ${cmdline:-<MISSING>})"
+  echo "rendered /srv/tftp/boot.ipxe -> ${uki} (cmdline: ${cmdline:-<MISSING>})"
 }
 
 if [ -n "${SERVER_IP:-}" ] && [ -n "${IMAGE_VERSION:-}" ]; then

serving/tftp/README.md

@@ -11,10 +11,16 @@ Flow for a PXE-only host:
 
 ```
 firmware PXE (PXEClient) --TFTP--> snponly.efi (iPXE)
-   iPXE re-DHCPs (user-class "iPXE") --> handed boot.ipxe (TFTP)
+   iPXE autoboot DHCP (user-class "iPXE") --> handed boot.ipxe (TFTP)
    boot.ipxe: imgfetch UKI over HTTP -> imgargs <real cmdline> -> boot
 ```
 
+> **Requires PortFast/edge on the switch port** (see the gotchas below). iPXE's
+> autoboot opens the NIC, which bounces the PHY; without PortFast the switch's STP
+> forwarding delay (~30 s) drops iPXE's DHCP and the boot fails. PortFast removes
+> the delay. (The earlier `autoexec.ipxe` + `ifopen` + DHCP-retry workaround was
+> removed once PortFast was identified as the real fix.)
+
 `boot.ipxe` is **rendered at container start** by the dnsmasq entrypoint; only the
 iPXE binary (`snponly.efi`) is supplied here. The script exists because of a sharp
 edge:
@@ -107,10 +113,16 @@ Hard-won findings from bringing up the first PXE-only physical host:
   ~30 s to every boot — PortFast removes the delay entirely.
 - **iPXE aborts the script on any unguarded command failure** (→ iPXE exits → the
   firmware restarts the whole PXE process, looking like "it doesn't retry"). Every
-  fallible step in `boot.ipxe`/`autoexec.ipxe` is therefore `||`-guarded.
-- **`autoexec.ipxe`** (rendered by the dnsmasq entrypoint) is fetched + run at
-  iPXE startup, *replacing* the default autoboot; that's where the `ifopen` +
-  DHCP-retry + `imgargs <real cmdline>` chain lives.
+  fallible step in `boot.ipxe` is therefore `||`-guarded.
+- **`boot.ipxe`** (rendered by the dnsmasq entrypoint, served as the `tag:ipxe`
+  DHCP bootfile) does `dhcp` + `imgfetch` UKI + `imgargs <real cmdline>` + `boot`.
+  The cmdline injection is needed only because **Secure Boot is OFF** (the stub
+  takes the loader's cmdline); under Secure Boot it's a no-op and `boot.ipxe`
+  could collapse to a plain `chain` of the UKI.
+- **Removed STP-era workaround:** an `autoexec.ipxe` that ran `ifopen net0` + a
+  DHCP-retry loop before autoboot was used to wait out STP. It's gone now that
+  **PortFast is the fix** — if you ever run on a switch you can't set PortFast on,
+  that ifopen+retry approach (in git history) is the fallback.
 
 ## Note