Networking/Ideas/NetworkNameResolution

Some ideas for name resolution in linux distributions

Resolve a host name to a list of network layer addresses

Input parameters:

• host
• family

Output parameters:

• List of sockaddr pointers (zero ports, zero protocols, etc)
• Canonical name (why?)

Unfortunately, gethostbyname() has been deprecated and getaddrinfo() is not a good alternative.

Use cases

• IP-based access lists
• Network layer testing tools
• Any tools working with non-TCP non-UDP protocols
• Possibly even tools working with TCP and UDP

Resolve a service name to a port number

Input parameters:

• service
• protocol (socktype?)

Output parameter:

• port
• protocol

Current status:

struct servent *getservbyname(const char *name, const char *proto);

struct servent {
    char  *s_name;       /* official service name */
    char **s_aliases;    /* alias list */
    int    s_port;       /* port number */
    char  *s_proto;      /* protocol to use */
}

Resolve an address for connect() or sendto()

Input parameters (network layer):

• host (IP address or some sort of host name)
• family (to implement -4 and -6 switches)

Input parameters (transport layer):

• socktype
• protocol
• service (TCP/UDP port number or service name)
• whether to use SRV records

Output parameters:

• List of sockaddr pointers
• Canonical name (why?)
• socktype
• protocol

Resolve an address for IP ACLs

Input parameters:

• host
• family

Output parameters:

• List of sockaddr pointers (zero ports, zero protocols, etc)
• Canonical name (why?)

How name resolution API should work

• *gethostinfo (name, family=0, flags=0) → list of sockaddr, canonical name
• *getservinfo (name, protocol=0, ?socktype=0) → port, protocol, ?socktype
• *getconninfo (host, service, family, socktype, protocol, flags) → list of sockaddr, ?socktype, ?protocol, canonical name