getaddrinfo "10 . 10 . 10 . 10"

I just noticed that if I f开发者_Python百科eed the string "10 . 10 . 10 . 10" to getaddrinfo i get back the address 0.0.0.10. The result is the same on both OS X (Lion) and Linux (CentOS 5.6). You can easily verify it yourself with:

$ curl 'http://10 . 10 . 10 . 10/' 
curl: (7) Failed to connect to 0.0.0.10: No route to host

Is there a specific reason for this behavior or should I consider it a bug? I would've expected it to fail to return any address.

Edit: Same result for "10 asdf", guess it's the space that makes it do that.

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POSIX allows a string consisting of a single number (in either decimal, hex with a leading 0x or 0X, or octal with a leading 0) to specify an IPv4 address: see the definition of inet_addr() (referenced by the definition of getaddrinfo() for the AF_INET address family).

As far as I can see, it doesn't say anything about how the input string is terminated, so the fact that it stops at a space is probably just an implementation detail; but "10" is certainly an allowable representation of an IPv4 address, if it's parsed by getaddrinfo() or inet_addr(). (Interestingly, this form is not allowed by inet_pton() with AF_INET - that only accepts the standard four-component form.)