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revert(vpcd/dhcp): drop AF_PACKET promisc wrapper, restore nclient4.New

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ecfbd4f swapped nclient4.New for openPromiscBridgeConn + NewWithConn to
catch unicast OFFER replies that bypass the bridge netdev. On dev hosts
where upstream honors the BOOTP BROADCAST flag, the wrapper regressed
DORA — public-IP allocation failed where main works. Reverting until
the promisc path is validated against both broadcast- and unicast-OFFER
servers.
This commit is contained in:
joshsiv-mulga
2026-04-30 14:26:43 +10:00
parent ecfbd4fd19
commit 82b0bdfd56
1 changed files with 3 additions and 52 deletions
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spinifex/services/vpcd/dhcp/nclient4.go
+3 -52
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@@ -3,46 +3,12 @@ package dhcp
import (
"context"
"fmt"
"net"
"time"
"github.com/insomniacslk/dhcp/dhcpv4"
"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
"github.com/mdlayher/packet"
"golang.org/x/sys/unix"
)
// dhcpClientPort is the IANA-assigned UDP port for DHCP clients.
const dhcpClientPort = 68
// openPromiscBridgeConn opens an AF_PACKET DGRAM socket on iface filtered
// to IPv4 and enables PACKET_MR_PROMISC on it. Equivalent to nclient4's
// own NewRawUDPConn but with promisc on.
//
// Why promisc: vpcd uses a synthetic per-tenant chaddr (e.g. 02:f3:...)
// that never matches the bridge's MAC. Many real-world DHCP servers
// ignore the BOOTP BROADCAST flag and reply with a unicast OFFER addressed
// to that chaddr. A Linux bridge floods unknown unicast to slave ports
// but does NOT pass it up to the bridge netdev unless IFF_PROMISC is set,
// so the AF_PACKET socket misses the OFFER and DORA times out. Promisc
// flips IFF_PROMISC for the lifetime of the socket (per-DORA), and the
// kernel refcounts it so it auto-clears on Close.
func openPromiscBridgeConn(iface string) (net.PacketConn, net.HardwareAddr, error) {
ifc, err := net.InterfaceByName(iface)
if err != nil {
return nil, nil, fmt.Errorf("lookup iface %s: %w", iface, err)
}
raw, err := packet.Listen(ifc, packet.Datagram, unix.ETH_P_IP, nil)
if err != nil {
return nil, nil, fmt.Errorf("packet.Listen on %s: %w", iface, err)
}
if err := raw.SetPromiscuous(true); err != nil {
_ = raw.Close()
return nil, nil, fmt.Errorf("set promisc on %s: %w", iface, err)
}
return nclient4.NewBroadcastUDPConn(raw, &net.UDPAddr{Port: dhcpClientPort}), ifc.HardwareAddr, nil
}
// NClient4Client is the production DHCP client backed by
// github.com/insomniacslk/dhcp/dhcpv4/nclient4. Each Acquire/Renew/Release
// opens an AF_PACKET socket on the target bridge for the duration of the
@@ -73,17 +39,12 @@ func (c *NClient4Client) Acquire(ctx context.Context, req AcquireRequest) (*Leas
return nil, fmt.Errorf("dhcp acquire: hw_addr is required")
}
conn, ifaceMAC, err := openPromiscBridgeConn(req.Bridge)
if err != nil {
return nil, fmt.Errorf("open promisc conn on %s: %w", req.Bridge, err)
}
client, err := nclient4.NewWithConn(conn, ifaceMAC,
client, err := nclient4.New(req.Bridge,
nclient4.WithHWAddr(req.HWAddr),
nclient4.WithTimeout(c.timeout),
nclient4.WithRetry(c.retry),
)
if err != nil {
_ = conn.Close()
return nil, fmt.Errorf("open nclient4 on %s: %w", req.Bridge, err)
}
defer func() { _ = client.Close() }()
@@ -104,17 +65,12 @@ func (c *NClient4Client) Renew(ctx context.Context, lease *Lease) (*Lease, error
return nil, fmt.Errorf("dhcp renew: %w", err)
}
conn, ifaceMAC, err := openPromiscBridgeConn(lease.Bridge)
if err != nil {
return nil, fmt.Errorf("open promisc conn on %s for renew: %w", lease.Bridge, err)
}
client, err := nclient4.NewWithConn(conn, ifaceMAC,
client, err := nclient4.New(lease.Bridge,
nclient4.WithHWAddr(lease.HWAddr),
nclient4.WithTimeout(c.timeout),
nclient4.WithRetry(c.retry),
)
if err != nil {
_ = conn.Close()
return nil, fmt.Errorf("open nclient4 on %s for renew: %w", lease.Bridge, err)
}
defer func() { _ = client.Close() }()
@@ -143,16 +99,11 @@ func (c *NClient4Client) Release(ctx context.Context, lease *Lease) error {
return fmt.Errorf("dhcp release: %w", err)
}
conn, ifaceMAC, err := openPromiscBridgeConn(lease.Bridge)
if err != nil {
return fmt.Errorf("open promisc conn on %s for release: %w", lease.Bridge, err)
}
client, err := nclient4.NewWithConn(conn, ifaceMAC,
client, err := nclient4.New(lease.Bridge,
nclient4.WithHWAddr(lease.HWAddr),
nclient4.WithTimeout(c.timeout),
)
if err != nil {
_ = conn.Close()
return fmt.Errorf("open nclient4 on %s for release: %w", lease.Bridge, err)
}
defer func() { _ = client.Close() }()