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CGNAT (Carrier-Grade NAT) is a technique used by ISPs to conserve IPv4 addresses. Instead of assigning a unique public IP to every customer, the ISP places many customers behind a shared NAT, then gives them all addresses from the reserved 100.64.0.0/10 range (RFC 6598) on their internal network. This means traffic from multiple customers exits through a small pool of public IPs - a second layer of NAT on top of whatever NAT the customer's own router does (hence "double NAT").
40 lines
1.5 KiB
Go
40 lines
1.5 KiB
Go
package tools
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import (
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"net"
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"net/url"
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)
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// cgnatRange is the CGNAT shared address space (RFC 6598), not covered by net.IP.IsPrivate().
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// CGNAT (Carrier-Grade NAT) is a technique used by ISPs to conserve IPv4 addresses. Instead of assigning a unique
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// public IP to every customer, the ISP places many customers behind a shared NAT, then gives them all addresses
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// from the reserved 100.64.0.0/10 range (RFC 6598) on their internal network.
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var cgnatRange = func() *net.IPNet {
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_, cidr, _ := net.ParseCIDR("100.64.0.0/10")
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return cidr
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}()
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// IsInternalIP checks if the given IP address is an internal IP address (e.g., loopback, private, link-local, or multicast).
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// IsLoopback — 127.0.0.0/8, ::1
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// IsPrivate — 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, fc00::/7
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// IsLinkLocalUnicast — 169.254.0.0/16, fe80::/10 (covers cloud metadata 169.254.169.254)
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// IsLinkLocalMulticast — 224.0.0.0/24, ff02::/16
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// IsUnspecified — 0.0.0.0, ::
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// IsMulticast — 224.0.0.0/4, ff00::/8
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// CGNAT — 100.64.0.0/10 (RFC 6598) (Carrier-Grade NAT)
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func IsInternalIP(ip net.IP) bool {
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return ip.IsLoopback() ||
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ip.IsPrivate() ||
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ip.IsLinkLocalUnicast() ||
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ip.IsLinkLocalMulticast() ||
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ip.IsUnspecified() ||
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ip.IsMulticast() ||
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cgnatRange.Contains(ip)
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}
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// IsValidLinkURL checks if the provided string is a valid URL with http or https scheme and a non-empty hostname.
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func IsValidLinkURL(str string) bool {
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u, err := url.Parse(str)
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return err == nil && (u.Scheme == "http" || u.Scheme == "https") && u.Hostname() != ""
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}
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