Update README.md

Remove the ipnet crate and implement a lightweight CidrRange struct
  that handles IPv4/IPv6 CIDR parsing and containment checks using
  bitwise masking. Adds tests for invalid prefixes and cross-family
  non-matching.

Cargo.lock

@@ -20,6 +20,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.102"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
+
 [[package]]
 name = "assert-json-diff"
 version = "2.0.2"
@@ -68,9 +74,9 @@ checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33"
 
 [[package]]
 name = "cc"
-version = "1.2.56"
+version = "1.2.57"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aebf35691d1bfb0ac386a69bac2fde4dd276fb618cf8bf4f5318fe285e821bb2"
+checksum = "7a0dd1ca384932ff3641c8718a02769f1698e7563dc6974ffd03346116310423"
 dependencies = [
  "find-msvc-tools",
  "shlex",
@@ -103,7 +109,7 @@ dependencies = [
 
 [[package]]
 name = "cloudflare-ddns"
-version = "2.0.2"
+version = "2.0.4"
 dependencies = [
  "chrono",
  "idna",
@@ -187,6 +193,12 @@ version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
+[[package]]
+name = "foldhash"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
+
 [[package]]
 name = "form_urlencoded"
 version = "1.2.2"
@@ -306,11 +318,24 @@ dependencies = [
  "cfg-if",
  "js-sys",
  "libc",
- "r-efi",
+ "r-efi 5.3.0",
  "wasip2",
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0de51e6874e94e7bf76d726fc5d13ba782deca734ff60d5bb2fb2607c7406555"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi 6.0.0",
+ "wasip2",
+ "wasip3",
+]
+
 [[package]]
 name = "h2"
 version = "0.4.13"
@@ -330,12 +355,27 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.15.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
+dependencies = [
+ "foldhash",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
 
+[[package]]
+name = "heck"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
+
 [[package]]
 name = "hermit-abi"
 version = "0.5.2"
@@ -555,6 +595,12 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "id-arena"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d3067d79b975e8844ca9eb072e16b31c3c1c36928edf9c6789548c524d0d954"
+
 [[package]]
 name = "idna"
 version = "1.1.0"
@@ -593,7 +639,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7714e70437a7dc3ac8eb7e6f8df75fd8eb422675fc7678aff7364301092b1017"
 dependencies = [
  "equivalent",
- "hashbrown",
+ "hashbrown 0.16.1",
+ "serde",
+ "serde_core",
 ]
 
 [[package]]
@@ -634,6 +682,12 @@ version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 
+[[package]]
+name = "leb128fmt"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
+
 [[package]]
 name = "libc"
 version = "0.2.183"
@@ -702,9 +756,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.21.3"
+version = "1.21.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
+checksum = "9f7c3e4beb33f85d45ae3e3a1792185706c8e16d043238c593331cc7cd313b50"
 
 [[package]]
 name = "percent-encoding"
@@ -742,6 +796,16 @@ dependencies = [
  "zerocopy",
 ]
 
+[[package]]
+name = "prettyplease"
+version = "0.2.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "479ca8adacdd7ce8f1fb39ce9ecccbfe93a3f1344b3d0d97f20bc0196208f62b"
+dependencies = [
+ "proc-macro2",
+ "syn",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.106"
@@ -821,6 +885,12 @@ version = "5.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
 
+[[package]]
+name = "r-efi"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8dcc9c7d52a811697d2151c701e0d08956f92b0e24136cf4cf27b57a6a0d9bf"
+
 [[package]]
 name = "rand"
 version = "0.9.2"
@@ -997,6 +1067,12 @@ version = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
 
+[[package]]
+name = "semver"
+version = "1.0.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d767eb0aabc880b29956c35734170f26ed551a859dbd361d140cdbeca61ab1e2"
+
 [[package]]
 name = "serde"
 version = "1.0.228"
@@ -1140,7 +1216,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
 dependencies = [
  "fastrand",
- "getrandom 0.3.4",
+ "getrandom 0.4.2",
  "once_cell",
  "rustix",
  "windows-sys 0.61.2",
@@ -1178,9 +1254,9 @@ dependencies = [
 
 [[package]]
 name = "tinyvec"
-version = "1.10.0"
+version = "1.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bfa5fdc3bce6191a1dbc8c02d5c8bffcf557bafa17c124c5264a458f1b0613fa"
+checksum = "3e61e67053d25a4e82c844e8424039d9745781b3fc4f32b8d55ed50f5f667ef3"
 dependencies = [
  "tinyvec_macros",
 ]
@@ -1317,6 +1393,12 @@ version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebc1c04c71510c7f702b52b7c350734c9ff1295c464a03335b00bb84fc54f853"
+
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -1365,6 +1447,15 @@ dependencies = [
  "wit-bindgen",
 ]
 
+[[package]]
+name = "wasip3"
+version = "0.4.0+wasi-0.3.0-rc-2026-01-06"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5428f8bf88ea5ddc08faddef2ac4a67e390b88186c703ce6dbd955e1c145aca5"
+dependencies = [
+ "wit-bindgen",
+]
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.114"
@@ -1424,6 +1515,40 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "wasm-encoder"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "990065f2fe63003fe337b932cfb5e3b80e0b4d0f5ff650e6985b1048f62c8319"
+dependencies = [
+ "leb128fmt",
+ "wasmparser",
+]
+
+[[package]]
+name = "wasm-metadata"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb0e353e6a2fbdc176932bbaab493762eb1255a7900fe0fea1a2f96c296cc909"
+dependencies = [
+ "anyhow",
+ "indexmap",
+ "wasm-encoder",
+ "wasmparser",
+]
+
+[[package]]
+name = "wasmparser"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47b807c72e1bac69382b3a6fb3dbe8ea4c0ed87ff5629b8685ae6b9a611028fe"
+dependencies = [
+ "bitflags",
+ "hashbrown 0.15.5",
+ "indexmap",
+ "semver",
+]
+
 [[package]]
 name = "web-sys"
 version = "0.3.91"
@@ -1705,6 +1830,88 @@ name = "wit-bindgen"
 version = "0.51.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d7249219f66ced02969388cf2bb044a09756a083d0fab1e566056b04d9fbcaa5"
+dependencies = [
+ "wit-bindgen-rust-macro",
+]
+
+[[package]]
+name = "wit-bindgen-core"
+version = "0.51.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea61de684c3ea68cb082b7a88508a8b27fcc8b797d738bfc99a82facf1d752dc"
+dependencies = [
+ "anyhow",
+ "heck",
+ "wit-parser",
+]
+
+[[package]]
+name = "wit-bindgen-rust"
+version = "0.51.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7c566e0f4b284dd6561c786d9cb0142da491f46a9fbed79ea69cdad5db17f21"
+dependencies = [
+ "anyhow",
+ "heck",
+ "indexmap",
+ "prettyplease",
+ "syn",
+ "wasm-metadata",
+ "wit-bindgen-core",
+ "wit-component",
+]
+
+[[package]]
+name = "wit-bindgen-rust-macro"
+version = "0.51.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0c0f9bfd77e6a48eccf51359e3ae77140a7f50b1e2ebfe62422d8afdaffab17a"
+dependencies = [
+ "anyhow",
+ "prettyplease",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wit-bindgen-core",
+ "wit-bindgen-rust",
+]
+
+[[package]]
+name = "wit-component"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9d66ea20e9553b30172b5e831994e35fbde2d165325bec84fc43dbf6f4eb9cb2"
+dependencies = [
+ "anyhow",
+ "bitflags",
+ "indexmap",
+ "log",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "wasm-encoder",
+ "wasm-metadata",
+ "wasmparser",
+ "wit-parser",
+]
+
+[[package]]
+name = "wit-parser"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ecc8ac4bc1dc3381b7f59c34f00b67e18f910c2c0f50015669dde7def656a736"
+dependencies = [
+ "anyhow",
+ "id-arena",
+ "indexmap",
+ "log",
+ "semver",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "unicode-xid",
+ "wasmparser",
+]
 
 [[package]]
 name = "writeable"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cloudflare-ddns"
-version = "2.0.3"
+version = "2.0.4"
 edition = "2021"
 description = "Access your home network remotely via a custom domain name without a static IP"
 license = "GPL-3.0"

README.md

@@ -28,6 +28,7 @@ Configure everything with environment variables. Supports notifications, heartbe
 - 🎨 **Pretty output with emoji** — Configurable emoji and verbosity levels
 - 🔒 **Zero-log IP detection** — Uses Cloudflare's [cdn-cgi/trace](https://www.cloudflare.com/cdn-cgi/trace) by default
 - 🏠 **CGNAT-aware local detection** — Filters out shared address space (100.64.0.0/10) and private ranges
+- 🚫 **Cloudflare IP rejection** — Optionally reject Cloudflare anycast IPs to prevent incorrect DNS updates
 - 🤏 **Tiny static binary** — ~1.9 MB Docker image built from scratch, zero runtime dependencies
 
 ## 🚀 Quick Start
@@ -87,6 +88,16 @@ Available providers:
 | `literal:<ips>` | 📌 Static IP addresses (comma-separated) |
 | `none` | 🚫 Disable this IP type |
 
+## 🚫 Cloudflare IP Rejection
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `REJECT_CLOUDFLARE_IPS` | `false` | Reject detected IPs that fall within Cloudflare's IP ranges |
+
+Some IP detection providers occasionally return a Cloudflare anycast IP instead of your real public IP. When this happens, your DNS record gets updated to point at Cloudflare infrastructure rather than your actual address.
+
+Setting `REJECT_CLOUDFLARE_IPS=true` prevents this. Each update cycle fetches [Cloudflare's published IP ranges](https://www.cloudflare.com/ips/) and skips any detected IP that falls within them. A warning is logged for every rejected IP.
+
 ## ⏱️ Scheduling
 
 | Variable | Default | Description |
@@ -210,6 +221,7 @@ Heartbeats are sent after each update cycle. On failure, a fail signal is sent.
 | `MANAGED_WAF_LIST_ITEMS_COMMENT_REGEX` | — | 🎯 Managed WAF items regex |
 | `DETECTION_TIMEOUT` | `5s` | ⏳ IP detection timeout |
 | `UPDATE_TIMEOUT` | `30s` | ⏳ API request timeout |
+| `REJECT_CLOUDFLARE_IPS` | `false` | 🚫 Reject Cloudflare anycast IPs |
 | `EMOJI` | `true` | 🎨 Enable emoji output |
 | `QUIET` | `false` | 🤫 Suppress info output |
 | `HEALTHCHECKS` | — | 💓 Healthchecks.io URL |

src/cf_ip_filter.rs

@@ -0,0 +1,237 @@
+use crate::pp::{self, PP};
+use reqwest::Client;
+use std::net::IpAddr;
+use std::time::Duration;
+
+const CF_IPV4_URL: &str = "https://www.cloudflare.com/ips-v4";
+const CF_IPV6_URL: &str = "https://www.cloudflare.com/ips-v6";
+
+/// A CIDR range parsed from "address/prefix" notation.
+struct CidrRange {
+    addr: IpAddr,
+    prefix_len: u8,
+}
+
+impl CidrRange {
+    fn parse(s: &str) -> Option<Self> {
+        let (addr_str, prefix_str) = s.split_once('/')?;
+        let addr: IpAddr = addr_str.parse().ok()?;
+        let prefix_len: u8 = prefix_str.parse().ok()?;
+        match addr {
+            IpAddr::V4(_) if prefix_len > 32 => None,
+            IpAddr::V6(_) if prefix_len > 128 => None,
+            _ => Some(Self { addr, prefix_len }),
+        }
+    }
+
+    fn contains(&self, ip: &IpAddr) -> bool {
+        match (self.addr, ip) {
+            (IpAddr::V4(net), IpAddr::V4(ip)) => {
+                let net_bits = u32::from(net);
+                let ip_bits = u32::from(*ip);
+                if self.prefix_len == 0 {
+                    return true;
+                }
+                let mask = !0u32 << (32 - self.prefix_len);
+                (net_bits & mask) == (ip_bits & mask)
+            }
+            (IpAddr::V6(net), IpAddr::V6(ip)) => {
+                let net_bits = u128::from(net);
+                let ip_bits = u128::from(*ip);
+                if self.prefix_len == 0 {
+                    return true;
+                }
+                let mask = !0u128 << (128 - self.prefix_len);
+                (net_bits & mask) == (ip_bits & mask)
+            }
+            _ => false,
+        }
+    }
+}
+
+/// Holds parsed Cloudflare CIDR ranges for IP filtering.
+pub struct CloudflareIpFilter {
+    ranges: Vec<CidrRange>,
+}
+
+impl CloudflareIpFilter {
+    /// Fetch Cloudflare IP ranges from their published URLs and parse them.
+    pub async fn fetch(client: &Client, timeout: Duration, ppfmt: &PP) -> Option<Self> {
+        let mut ranges = Vec::new();
+
+        for url in [CF_IPV4_URL, CF_IPV6_URL] {
+            match client.get(url).timeout(timeout).send().await {
+                Ok(resp) if resp.status().is_success() => match resp.text().await {
+                    Ok(body) => {
+                        for line in body.lines() {
+                            let line = line.trim();
+                            if line.is_empty() {
+                                continue;
+                            }
+                            match CidrRange::parse(line) {
+                                Some(range) => ranges.push(range),
+                                None => {
+                                    ppfmt.warningf(
+                                        pp::EMOJI_WARNING,
+                                        &format!(
+                                            "Failed to parse Cloudflare IP range '{line}'"
+                                        ),
+                                    );
+                                }
+                            }
+                        }
+                    }
+                    Err(e) => {
+                        ppfmt.warningf(
+                            pp::EMOJI_WARNING,
+                            &format!("Failed to read Cloudflare IP ranges from {url}: {e}"),
+                        );
+                        return None;
+                    }
+                },
+                Ok(resp) => {
+                    ppfmt.warningf(
+                        pp::EMOJI_WARNING,
+                        &format!(
+                            "Failed to fetch Cloudflare IP ranges from {url}: HTTP {}",
+                            resp.status()
+                        ),
+                    );
+                    return None;
+                }
+                Err(e) => {
+                    ppfmt.warningf(
+                        pp::EMOJI_WARNING,
+                        &format!("Failed to fetch Cloudflare IP ranges from {url}: {e}"),
+                    );
+                    return None;
+                }
+            }
+        }
+
+        if ranges.is_empty() {
+            ppfmt.warningf(
+                pp::EMOJI_WARNING,
+                "No Cloudflare IP ranges loaded; skipping filter",
+            );
+            return None;
+        }
+
+        ppfmt.infof(
+            pp::EMOJI_DETECT,
+            &format!("Loaded {} Cloudflare IP ranges for filtering", ranges.len()),
+        );
+
+        Some(Self { ranges })
+    }
+
+    /// Parse ranges from raw text lines (for testing).
+    #[cfg(test)]
+    pub fn from_lines(lines: &str) -> Option<Self> {
+        let ranges: Vec<CidrRange> = lines
+            .lines()
+            .filter_map(|l| {
+                let l = l.trim();
+                if l.is_empty() {
+                    None
+                } else {
+                    CidrRange::parse(l)
+                }
+            })
+            .collect();
+        if ranges.is_empty() {
+            None
+        } else {
+            Some(Self { ranges })
+        }
+    }
+
+    /// Check if an IP address falls within any Cloudflare range.
+    pub fn contains(&self, ip: &IpAddr) -> bool {
+        self.ranges.iter().any(|net| net.contains(ip))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::net::{Ipv4Addr, Ipv6Addr};
+
+    const SAMPLE_RANGES: &str = "\
+173.245.48.0/20
+103.21.244.0/22
+103.22.200.0/22
+104.16.0.0/13
+2400:cb00::/32
+2606:4700::/32
+";
+
+    #[test]
+    fn test_parse_ranges() {
+        let filter = CloudflareIpFilter::from_lines(SAMPLE_RANGES).unwrap();
+        assert_eq!(filter.ranges.len(), 6);
+    }
+
+    #[test]
+    fn test_contains_cloudflare_ipv4() {
+        let filter = CloudflareIpFilter::from_lines(SAMPLE_RANGES).unwrap();
+        // 104.16.0.1 is within 104.16.0.0/13
+        let ip: IpAddr = IpAddr::V4(Ipv4Addr::new(104, 16, 0, 1));
+        assert!(filter.contains(&ip));
+    }
+
+    #[test]
+    fn test_rejects_non_cloudflare_ipv4() {
+        let filter = CloudflareIpFilter::from_lines(SAMPLE_RANGES).unwrap();
+        // 203.0.113.42 is a documentation IP, not Cloudflare
+        let ip: IpAddr = IpAddr::V4(Ipv4Addr::new(203, 0, 113, 42));
+        assert!(!filter.contains(&ip));
+    }
+
+    #[test]
+    fn test_contains_cloudflare_ipv6() {
+        let filter = CloudflareIpFilter::from_lines(SAMPLE_RANGES).unwrap();
+        // 2606:4700::1 is within 2606:4700::/32
+        let ip: IpAddr = IpAddr::V6(Ipv6Addr::new(0x2606, 0x4700, 0, 0, 0, 0, 0, 1));
+        assert!(filter.contains(&ip));
+    }
+
+    #[test]
+    fn test_rejects_non_cloudflare_ipv6() {
+        let filter = CloudflareIpFilter::from_lines(SAMPLE_RANGES).unwrap();
+        // 2001:db8::1 is a documentation address, not Cloudflare
+        let ip: IpAddr = IpAddr::V6(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1));
+        assert!(!filter.contains(&ip));
+    }
+
+    #[test]
+    fn test_empty_input() {
+        assert!(CloudflareIpFilter::from_lines("").is_none());
+        assert!(CloudflareIpFilter::from_lines("  \n  \n").is_none());
+    }
+
+    #[test]
+    fn test_edge_of_range() {
+        let filter = CloudflareIpFilter::from_lines("104.16.0.0/13").unwrap();
+        // First IP in range
+        assert!(filter.contains(&IpAddr::V4(Ipv4Addr::new(104, 16, 0, 0))));
+        // Last IP in range (104.23.255.255)
+        assert!(filter.contains(&IpAddr::V4(Ipv4Addr::new(104, 23, 255, 255))));
+        // Just outside range (104.24.0.0)
+        assert!(!filter.contains(&IpAddr::V4(Ipv4Addr::new(104, 24, 0, 0))));
+    }
+
+    #[test]
+    fn test_invalid_prefix_rejected() {
+        assert!(CidrRange::parse("10.0.0.0/33").is_none());
+        assert!(CidrRange::parse("::1/129").is_none());
+        assert!(CidrRange::parse("not-an-ip/24").is_none());
+    }
+
+    #[test]
+    fn test_v4_does_not_match_v6() {
+        let filter = CloudflareIpFilter::from_lines("104.16.0.0/13").unwrap();
+        let ip: IpAddr = IpAddr::V6(Ipv6Addr::new(0x2606, 0x4700, 0, 0, 0, 0, 0, 1));
+        assert!(!filter.contains(&ip));
+    }
+}

src/config.rs

@@ -89,6 +89,7 @@ pub struct AppConfig {
     pub managed_waf_comment_regex: Option<regex::Regex>,
     pub detection_timeout: Duration,
     pub update_timeout: Duration,
+    pub reject_cloudflare_ips: bool,
     pub dry_run: bool,
     pub emoji: bool,
     pub quiet: bool,
@@ -439,6 +440,7 @@ fn legacy_to_app_config(legacy: LegacyConfig, dry_run: bool, repeat: bool) -> Ap
         managed_waf_comment_regex: None,
         detection_timeout: Duration::from_secs(5),
         update_timeout: Duration::from_secs(30),
+        reject_cloudflare_ips: false,
         dry_run,
         emoji: false,
         quiet: false,
@@ -509,6 +511,7 @@ pub fn load_env_config(ppfmt: &PP) -> Result<AppConfig, String> {
 
     let emoji = getenv_bool("EMOJI", true);
     let quiet = getenv_bool("QUIET", false);
+    let reject_cloudflare_ips = getenv_bool("REJECT_CLOUDFLARE_IPS", false);
 
     // Validate: must have at least one update target
     if domains.is_empty() && waf_lists.is_empty() {
@@ -559,6 +562,7 @@ pub fn load_env_config(ppfmt: &PP) -> Result<AppConfig, String> {
         managed_waf_comment_regex,
         detection_timeout,
         update_timeout,
+        reject_cloudflare_ips,
         dry_run: false, // Set later from CLI args
         emoji,
         quiet,
@@ -659,6 +663,10 @@ pub fn print_config_summary(config: &AppConfig, ppfmt: &PP) {
         inner.infof("", "Delete on stop: enabled");
     }
 
+    if config.reject_cloudflare_ips {
+        inner.infof("", "Reject Cloudflare IPs: enabled");
+    }
+
     if let Some(ref comment) = config.record_comment {
         inner.infof("", &format!("Record comment: {comment}"));
     }
@@ -1190,6 +1198,7 @@ mod tests {
             managed_waf_comment_regex: None,
             detection_timeout: Duration::from_secs(5),
             update_timeout: Duration::from_secs(30),
+            reject_cloudflare_ips: false,
             dry_run: false,
             emoji: false,
             quiet: false,
@@ -1223,6 +1232,7 @@ mod tests {
             managed_waf_comment_regex: None,
             detection_timeout: Duration::from_secs(5),
             update_timeout: Duration::from_secs(30),
+            reject_cloudflare_ips: false,
             dry_run: false,
             emoji: false,
             quiet: false,
@@ -1881,6 +1891,7 @@ mod tests {
             managed_waf_comment_regex: None,
             detection_timeout: Duration::from_secs(5),
             update_timeout: Duration::from_secs(30),
+            reject_cloudflare_ips: false,
             dry_run: false,
             emoji: false,
             quiet: false,
@@ -1916,6 +1927,7 @@ mod tests {
             managed_waf_comment_regex: None,
             detection_timeout: Duration::from_secs(5),
             update_timeout: Duration::from_secs(30),
+            reject_cloudflare_ips: false,
             dry_run: false,
             emoji: false,
             quiet: true,
@@ -1948,6 +1960,7 @@ mod tests {
             managed_waf_comment_regex: None,
             detection_timeout: Duration::from_secs(5),
             update_timeout: Duration::from_secs(30),
+            reject_cloudflare_ips: false,
             dry_run: false,
             emoji: false,
             quiet: false,

src/main.rs

@@ -1,3 +1,4 @@
+mod cf_ip_filter;
 mod cloudflare;
 mod config;
 mod domain;

src/updater.rs

@@ -1,3 +1,4 @@
+use crate::cf_ip_filter::CloudflareIpFilter;
 use crate::cloudflare::{CloudflareHandle, SetResult};
 use crate::config::{AppConfig, LegacyCloudflareEntry, LegacySubdomainEntry};
 use crate::domain::make_fqdn;
@@ -65,6 +66,49 @@ pub async fn update_once(
             }
         }
 
+        // Filter out Cloudflare IPs if enabled
+        if config.reject_cloudflare_ips {
+            if let Some(cf_filter) =
+                CloudflareIpFilter::fetch(&detection_client, config.detection_timeout, ppfmt).await
+            {
+                for (ip_type, ips) in detected_ips.iter_mut() {
+                    let before_count = ips.len();
+                    ips.retain(|ip| {
+                        if cf_filter.contains(ip) {
+                            ppfmt.warningf(
+                                pp::EMOJI_WARNING,
+                                &format!(
+                                    "Rejected {ip}: matches Cloudflare IP range ({})",
+                                    ip_type.describe()
+                                ),
+                            );
+                            false
+                        } else {
+                            true
+                        }
+                    });
+                    if ips.is_empty() && before_count > 0 {
+                        ppfmt.warningf(
+                            pp::EMOJI_WARNING,
+                            &format!(
+                                "All detected {} addresses were Cloudflare IPs; skipping updates for this type",
+                                ip_type.describe()
+                            ),
+                        );
+                        messages.push(Message::new_fail(&format!(
+                            "All {} addresses rejected (Cloudflare IPs)",
+                            ip_type.describe()
+                        )));
+                    }
+                }
+            } else {
+                ppfmt.warningf(
+                    pp::EMOJI_WARNING,
+                    "Could not fetch Cloudflare IP ranges; skipping filter",
+                );
+            }
+        }
+
         // Update DNS records (env var mode - domain-based)
         for (ip_type, domains) in &config.domains {
             let ips = detected_ips.get(ip_type).cloned().unwrap_or_default();
@@ -693,6 +737,7 @@ mod tests {
             managed_waf_comment_regex: None,
             detection_timeout: Duration::from_secs(5),
             update_timeout: Duration::from_secs(5),
+            reject_cloudflare_ips: false,
             dry_run,
             emoji: false,
             quiet: true,