coredns/plugin/proxyproto

proxyproto

Name

proxyproto - add PROXY protocol support.

Description

This plugin adds support for the PROXY protocol version 1 and 2. It allows CoreDNS to receive connections from a load balancer or proxy that uses the PROXY protocol to forward the original client's IP address and port information.

Syntax

proxyproto {
    allow <CIDR...>
    default <use|ignore|reject|skip>
    udp_session_tracking <duration> [max_sessions]
    tlv_metadata
}

If allow is unspecified, PROXY protocol headers are accepted from all IP addresses. The default option controls how connections from sources not listed in allow are handled. If default is unspecified, it defaults to ignore. The possible values are:

• use: accept and use PROXY protocol headers from these sources
• ignore: accept and ignore PROXY protocol headers from other sources
• reject: reject connections with PROXY protocol headers from other sources
• skip: skip PROXY protocol processing for connections from other sources, treating them as normal connections preserving the PROXY protocol headers.

The udp_session_tracking <duration> [max_sessions] option enables UDP session state tracking for Cloudflare Spectrum's PROXY Protocol v2 over UDP. Spectrum sends the PPv2 header as a standalone first datagram (with no DNS payload). Subsequent datagrams from the same client arrive without any header. When this option is set to a positive duration, the real client address from the header-only datagram is cached (keyed by the Spectrum-side remote address) for that duration and automatically applied to all subsequent headerless datagrams within that window. The TTL is refreshed on each matching packet. The optional max_sessions argument caps the number of concurrent sessions in the LRU cache (default: 10240). This option has no effect for TCP connections.

The tlv_metadata option exposes the PROXY Protocol v2 TLV (Type-Length-Value) vector from the header to downstream plugins via the metadata plugin. When set, and the metadata plugin is enabled, the raw TLV vector is published under the label proxyproto/tlv as a hex-encoded string. Consumers decode the hex and split it with proxyproto.SplitTLVs from github.com/pires/go-proxyproto to read individual TLVs (e.g. the AWS VPC endpoint ID, SSL client CN, or vendor-specific custom TLVs). This option is opt-in: without it, TLVs are not captured and no extra per-connection processing occurs. It applies to all transports: dns:// (UDP and TCP), tls:// (DoT), https:// (DoH), grpc://, quic:// (DoQ), and https3:// (DoH3).

For the QUIC-based transports (quic:// and https3://), the PPv2 header arrives as a standalone first datagram ahead of the QUIC handshake, so TLV capture additionally requires udp_session_tracking to be enabled; the cached session links the subsequent headerless QUIC datagrams to the header's source and TLVs.

Metadata

When the tlv_metadata option and the metadata plugin are both enabled, the following metadata label is made available:

• proxyproto/tlv: the raw PPv2 TLV vector, hex-encoded. Only set when the request's connection carried a PPv2 header with at least one TLV.

Examples

In this configuration, we allow PROXY protocol connections from all IP addresses:

. {
    proxyproto
    forward . /etc/resolv.conf
}

In this configuration, we only allow PROXY protocol connections from the specified CIDR ranges and ignore proxy protocol headers from other sources:

. {
    proxyproto {
        allow 192.168.1.1/32 192.168.0.1/32
    }
    forward . /etc/resolv.conf
}

In this configuration, we only allow PROXY protocol headers from the specified CIDR ranges and reject connections without valid PROXY protocol headers from those sources:

. {
    proxyproto {
        allow 192.168.1.1/32
        default reject
    }
    forward . /etc/resolv.conf
}

In this configuration, we enable UDP session tracking for Cloudflare Spectrum's PPv2-over-UDP with a 28-second TTL (slightly shorter than Spectrum's 30-second UDP idle timeout) and the default session cap of 10240:

. {
    proxyproto {
        allow 192.168.1.1/32
        udp_session_tracking 28s
    }
    forward . /etc/resolv.conf
}

In this configuration, the session cap is raised to 20480:

. {
    proxyproto {
        allow 192.168.1.1/32
        udp_session_tracking 28s 20000
    }
    forward . /etc/resolv.conf
}

In this configuration, PPv2 TLVs are exposed to downstream plugins as metadata. The metadata plugin must also be enabled. Here the log plugin records the raw TLV vector:

. {
    metadata
    proxyproto {
        allow 192.168.1.1/32
        tlv_metadata
    }
    forward . /etc/resolv.conf
    log . "{remote} {/proxyproto/tlv}"
}