sockaddr definition

[fordcars]

In socket.h, sockaddr is defined as follows:

struct sockaddr {
	sa_family_t sa_family;
	char        sa_data[];
};

However, according to Linux man pages, it should be defined as follows:

struct sockaddr {
	sa_family_t sa_family;
	char        sa_data[14];
  }

This can cause out-of-bounds memory access when casting between sockaddr and sockaddr_in, which is often done. For reference, here is how sockaddr_in is defined in libctru in.h :

struct sockaddr_in {
	sa_family_t     sin_family;
	in_port_t       sin_port;
	struct in_addr  sin_addr;
	unsigned char   sin_zero[8];
};

I am no socket expert, so I'm not sure if this is intended or not.
Thank you!

[mtheall]

You should never use sockaddr for storage; it's only for interface. Use sockaddr_in or sockaddr_storage.

[fordcars]

You should never use sockaddr for storage; it's only for interface. Use sockaddr_in or sockaddr_storage.

I think you are correct. I am currently porting a rather large networking library, and sockaddr is used as storage everywhere, so I wasn't sure. However, as you mention, the man pages say:

The only purpose of this structure is to cast the structure pointer passed in addr in order to avoid compiler warnings.

I guess the original authors wrongly used sockaddr as storage. However, this library has been used for at least a decade on a wide variety of systems and consoles; was it once considered acceptable to use sockaddr as storage?

Thanks!

[mtheall]

was it once considered acceptable to use sockaddr as storage?

No. That's the whole purpose of sockaddr_storage. It's large enough to hold any type that socket functions which take a sockaddr* as a parameter.

It would be reasonable libctru to make sockaddr as large as sockaddr_in since that's the only socket type it supports.