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Proxy

You can forward HTTP and network traffic to Gateway for logging and filtering. Gateway can proxy both outbound traffic and traffic directed to resources connected via a Cloudflare Tunnel, GRE tunnel, or IPsec tunnel. When a user connects to the Gateway proxy, Gateway will accept the connection and establish a new, separate connection to the origin server.

The Gateway proxy is required for filtering HTTP and network traffic via the WARP client in Gateway with WARP mode. To proxy HTTP traffic without deploying the WARP client, you can configure PAC files on your devices.

Proxy algorithm

Gateway uses the Happy Eyeballs algorithm ↗ to proxy traffic in the following order:

  1. The user's browser initiates the TCP handshake by sending Gateway a TCP SYN segment.
  2. Gateway sends a SYN segment to the origin server.
  3. If the origin server sends a SYN-ACK segment back, Gateway establishes separate TCP connections between the user and Gateway and between Gateway and the origin server.
  4. Gateway inspects and filters traffic received from the user.
  5. If the traffic passes inspection, Gateway proxies traffic bidirectionally between the user and the origin server.
flowchart TD
    %% Accessibility
    accTitle: How Gateway proxy works
    accDescr: Flowchart describing how the Gateway proxy uses the Happy Eyeballs algorithm to establish TCP connections and proxy user traffic.

    %% Flowchart
    A[User's device sends TCP SYN to Gateway] --> B[Gateway sends TCP SYN to origin server]
    B --> C{{Origin server responds with TCP SYN-ACK?}}
    C -->|Yes| E[TCP handshakes completed]
    C -->|No| D[Connection fails]
    E --> F{{Connection allowed?}}
    F -->|Yes| G[Gateway proxies traffic bidirectionally]
    F -->|No| H[Connection blocked by firewall policies]

    %% Styling
    style D stroke:#D50000
    style G stroke:#00C853
    style H stroke:#D50000

Supported protocols

Gateway supports proxying TCP, UDP, and ICMP traffic.

TCP

When the proxy is enabled, Gateway will always forward TCP traffic.

By default, TCP connection attempts will timeout after 30 seconds and idle connections will disconnect after 8 hours.

UDP

The UDP proxy forwards UDP traffic such as VoIP, internal DNS requests, and thick client applications.

When the UDP proxy is enabled, Gateway will force all HTTP/3 traffic to HTTP/2 to allow inspection. Otherwise, HTTP/3 traffic will bypass inspection. For more information, refer to HTTP/3 inspection.

ICMP Beta

The ICMP proxy forwards traffic for diagnostic tools such as ping and traceroute.

Allow ICMP traffic through cloudflared

To use the ICMP proxy with Cloudflare Tunnel, you may need to configure the cloudflared host to allow ICMP traffic through cloudflared.

  1. Ensure that ping_group_range includes the Group ID (GID) of the user running cloudflared:

    a. Find the user that owns the cloudflared process:

    Terminal window
    ps -aux | grep cloudflared
    johndoe         407  0.8  1.7 1259904 35296 ?       Ssl  21:02   0:00 /usr/bin/cloudflared --no-autoupdate tunnel run --token eyJhI...

    b. Get the Group ID of the cloudflared user:

    Terminal window
    id -g johndoe
    10001

    c. Determine the Group IDs that are allowed to use ICMP:

    Terminal window
    sudo sysctl net.ipv4.ping_group_range
    net.ipv4.ping_group_range= 0 10000

    d. Either add the user to a group within that range, or update the range to encompass a group the user is already in. To update ping_group_range:

    Terminal window
    echo 0 10001 | sudo tee /proc/sys/net/ipv4/ping_group_range

    e. To make the change persist on reboot, update your systcl parameters:

    Terminal window
    echo "net.ipv4.ping_group_range = 0 10001" | sudo tee -a /etc/sysctl.d/99-cloudflared.conf

  2. If you are running multiple network interfaces (for example, eth0 and eth1), configure cloudflared to use the external Internet-facing interface:

    Terminal window
    cloudflared tunnel run --icmpv4-src <IP of primary interface>

Turn on the Gateway proxy

  1. In Zero Trust ↗, go to Settings > Network.
  2. In Firewall, turn on Proxy.
  3. Select TCP.
  4. (Optional) Depending on your use case, you can select UDP and/or ICMP.