Function is_ipv4_literal_candidate 

pub fn is_ipv4_literal_candidate(s: &str) -> bool

Returns true when the input looks like a dotted IPv4 literal candidate.

This is a fast pre-filter: it checks that the string contains only digits and dots, and has at least one dot. It does NOT validate the actual address format — use parse_ipv4_literal for that.

Example

assert!(is_ipv4_literal_candidate("192.168.1.1"));
assert!(!is_ipv4_literal_candidate("hello"));
assert!(is_ipv4_literal_candidate("999.999.999.999")); // passes filter, fails parse