lab/labsim/ovs.sh

#!/bin/bash
# Open vSwitch fabric for labsim — the "switch" the whole sim hangs off.
#
# Why OVS and not a Linux bridge: a Linux bridge cannot do LACP at all, and its
# VLAN support is awkward to drive from libvirt. OVS gives real 802.1Q access
# and trunk ports plus real LACP bonds, so a router VM can run the SAME bond0 +
# vif config as the production VP2440s instead of an approximation.
#
# Layout:
#   ovs-labsim            the switch
#     ├─ vm ports         access ports, tag=<vlan>       (micro VM per VLAN)
#     ├─ hostv<vlan>      internal ports, tag=<vlan>     (host leg, for SSH)
#     └─ lag-vyos         LACP bond, trunk of all VLANs  (router under test)
# shellcheck disable=SC2034

OVS_BR="${OVS_BR:-ovs-labsim}"
OVS_NET="${OVS_NET:-labsim-ovs}"          # libvirt network wrapping the bridge
LAG_NAME="${LAG_NAME:-lag-vyos}"

ovs() { sudo ovs-vsctl "$@"; }

ovs_require() {
  command -v ovs-vsctl >/dev/null 2>&1 || die "openvswitch not installed (dnf install openvswitch)"
  systemctl is-active --quiet openvswitch || sudo systemctl start openvswitch \
    || die "could not start openvswitch"
}

# All VLAN ids from the config, comma separated — used for trunk ports.
vlan_id_list() {
  local ids=()
  for entry in "${SELECTED[@]}"; do ids+=("${entry%%:*}"); done
  (IFS=,; echo "${ids[*]}")
}

ovs_up() {
  ovs_require
  ovs --may-exist add-br "$OVS_BR"

  # Host leg per VLAN: an OVS internal port carrying that VLAN's tag, given the
  # .2 address. This is how you SSH to the VMs. It is deliberately NOT their
  # default route (.1 is), so inter-VLAN tests exercise the router, not the
  # host's routing table.
  for entry in "${SELECTED[@]}"; do
    IFS=: read -r vid _name prefix _real <<<"$entry"
    local port="hostv${vid}"
    ovs --may-exist add-port "$OVS_BR" "$port" tag="$vid" \
      -- set interface "$port" type=internal
    sudo ip link set "$port" up 2>/dev/null || true
    sudo ip addr replace "${prefix}.2/24" dev "$port"
  done

  ovs_define_libvirt_net
}

# A libvirt network that hands out OVS ports: one portgroup per VLAN (access)
# plus a trunk portgroup for the router.
ovs_define_libvirt_net() {
  local pg="" ids
  for entry in "${SELECTED[@]}"; do
    IFS=: read -r vid name _p _r <<<"$entry"
    pg+="  <portgroup name='vlan${vid}'>
    <vlan><tag id='${vid}'/></vlan>
  </portgroup>
"
  done

  # Trunk: VLAN 1 native/untagged, everything else tagged — the production
  # shape. libvirt expresses this declaratively via nativeMode='untagged'
  # (see libvirt formatnetwork.html), so it does not need fixing up by hand.
  # It also matters functionally: LACPDUs are untagged, and a trunk with no
  # native VLAN has nowhere to put them.
  local trunk="  <portgroup name='trunk'>
    <vlan trunk='yes'>
"
  for entry in "${SELECTED[@]}"; do
    IFS=: read -r vid _n _p _r <<<"$entry"
    if [ "$vid" = "1" ]; then
      trunk+="      <tag id='1' nativeMode='untagged'/>
"
    else
      trunk+="      <tag id='${vid}'/>
"
    fi
  done
  trunk+="    </vlan>
  </portgroup>
"

  local xml="<network>
  <name>${OVS_NET}</name>
  <forward mode='bridge'/>
  <bridge name='${OVS_BR}'/>
  <virtualport type='openvswitch'/>
${pg}${trunk}</network>"

  if virsh_q net-info "$OVS_NET" >/dev/null 2>&1; then
    virsh_q net-destroy "$OVS_NET" >/dev/null 2>&1 || true
    virsh_q net-undefine "$OVS_NET" >/dev/null 2>&1 || true
  fi
  echo "$xml" | virsh_q net-define /dev/stdin >/dev/null
  virsh_q net-start "$OVS_NET" >/dev/null
  log "libvirt network $OVS_NET bound to $OVS_BR (access portgroups + trunk)"
}

# Replace the router VM's two individual OVS ports with a single LACP bond.
# libvirt attaches each NIC separately; only ovs-vsctl can bond them, and the
# taps only exist once the VM is running — so this runs post-start.
ovs_bond_router() {
  local vm="$1"
  local taps
  # NB: domiflist indents its rows, so anchor on the FIELD not the line —
  # /^vnet/ silently matches nothing and the bond never gets built.
  taps="$(virsh_q domiflist "$vm" 2>/dev/null | awk '$1 ~ /^vnet/ {print $1}')"
  local count; count="$(echo "$taps" | grep -c .)"
  [ "$count" -eq 2 ] || { warn "router $vm has $count tap(s), expected 2 — skipping bond"; return 1; }

  # Already bonded? (idempotent re-runs)
  if ovs list-ports "$OVS_BR" 2>/dev/null | grep -qx "$LAG_NAME"; then
    log "LACP bond $LAG_NAME already present"
    return 0
  fi

  local t1 t2; t1="$(echo "$taps" | sed -n 1p)"; t2="$(echo "$taps" | sed -n 2p)"
  log "bonding $t1 + $t2 into $LAG_NAME (LACP active, balance-tcp)"
  ovs del-port "$OVS_BR" "$t1" 2>/dev/null || true
  ovs del-port "$OVS_BR" "$t2" 2>/dev/null || true

  # bond_mode=balance-tcp is REQUIRED: OVS defaults a bond to active-backup,
  # which does not speak LACP at all (confirmed on ovs-discuss). It is also the
  # equivalent of VyOS's 802.3ad + layer2+3 hashing.
  #
  # lacp-fallback-ab breaks a genuine deadlock: OVS keeps members disabled
  # until LACP negotiates, while the partner needs carrier before it will send
  # LACPDUs. Falling back to active-backup brings the links up so negotiation
  # can start.
  #
  # native-untagged + tag=1 carries the untagged LACPDUs and the management
  # VLAN, matching production. libvirt's portgroup VLAN config does NOT apply
  # here — the bond is a port libvirt never created — so set it inline.
  local tagged; tagged="$(vlan_id_list | tr ',' '\n' | grep -vx 1 | paste -sd, -)"
  ovs add-bond "$OVS_BR" "$LAG_NAME" "$t1" "$t2" \
      lacp=active bond_mode=balance-tcp \
      vlan_mode=native-untagged tag=1 trunks="$tagged" \
    -- set port "$LAG_NAME" other_config:lacp-time=fast \
    -- set port "$LAG_NAME" other_config:lacp-fallback-ab=true
}

ovs_bond_status() {
  echo "--- ovs bond ---"
  sudo ovs-appctl bond/show "$LAG_NAME" 2>/dev/null | grep -E "bond_mode|lacp_status|^member|may_enable" || echo "(no bond)"
  echo "--- lacp ---"
  sudo ovs-appctl lacp/show "$LAG_NAME" 2>/dev/null | grep -E "status|aggregation key|^member|attached" || true
}

ovs_down() {
  virsh_q net-destroy "$OVS_NET" >/dev/null 2>&1 || true
  virsh_q net-undefine "$OVS_NET" >/dev/null 2>&1 || true
  if command -v ovs-vsctl >/dev/null 2>&1; then
    ovs --if-exists del-br "$OVS_BR" 2>/dev/null || true
  fi
}