Menu Close

What is struct Addrinfo?

What is struct Addrinfo?

The addrinfo structure describes address information for use with TCP/IP. To get this information, call getaddrinfo(); to free a linked list of these structures, call freeaddrinfo(). The addrinfo structure includes these members: ai_flags. Flags.

What does getaddrinfo return?

The getaddrinfo() function translates the name of a service location (for example, a host name) and/or service name and returns a set of socket addresses and associated information to be used in creating a socket with which to address the specified service.

What is Ai_flags?

ai_flags contains the AI_NUMERICHOST flag, then node must be a numerical network address. The AI_NUMERICHOST flag suppresses any potentially lengthy network host address lookups. ai_flags, and node is NULL, then the returned socket addresses will be suitable for bind(2)ing a socket that will accept(2) connections.

What is Ai_family?

ptr->ai_family is just an integer, a member of a struct addrinfo. ( And if you are wondering about the particular syntax of ptr-> , you can go through this question ), it will have a value of either AF_INET or AF_INET6 (Or in theory any other supported protocol)

Does getaddrinfo use DNS?

getaddrinfo() uses the DNS protocol to talk to your name servers, which are configured using their IP address.

Why do we need getaddrinfo?

getaddrinfo() converts human-readable text strings representing hostnames or IP addresses into a dynamically allocated linked list of struct addrinfo structures. The function prototype for this function is specified as follows: 0.1″, or NULL, in which case the address 0.0.

Does getaddrinfo allocate memory?

freeaddrinfo() This function frees the memory allocated by function getaddrinfo(). As the result of the latter is a linked list of addrinfo structures starting at the address ai, freeaddrinfo() loops through the list and frees each one in turn.

Is getaddrinfo a Posix?

The getaddrinfo() and getnameinfo() functions are part of the POSIX standard application programming interface (API) for converting domain name system (DNS) hostnames and IP addresses between their human-readable text representations and structured binary formats for the operating system’s networking API.

Is getaddrinfo thread safe?

getaddrinfo() is indeed thread-safe. This is required by RFC 3493 Section 6.1: Functions getaddrinfo() and freeaddrinfo() must be thread-safe.

Why is Gethostbyname not thread safe?

This is because gethostbyname() usually uses a static buffer internally, that is why you have to copy the data before calling gethostbyname() again.

What is socket Gethostbyname?

The gethostbyname function returns a pointer to a hostent structure—a structure allocated by Windows Sockets. The hostent structure contains the results of a successful search for the host specified in the name parameter.

Where can I find the IPv6 address of a struct?

If you examine res->ai_next, you should find the IPv6 entry. As for the integer fields in a struct addrinfo, they correspond to predefined constants with implementation-defined values, and the integer values themselves are not of general interest.

Does Ai_addrconfig return IPv4 or IPv6 addresses?

If AI_ADDRCONFIG flag is specified, IPv4 addresses shall be returned only if an IPv4 address is configured on the local system, and IPv6 addresses shall be returned only if an IPv6 address is configured on the local system. The IPv4 or IPv6 loopback address is not considered a valid global address.

What is the host address string in IPv4?

For the Internet protocol, the numeric host address string is a dotted-decimal IPv4 address or an IPv6 hex address. A pointer to a NULL -terminated ANSI string that contains either a service name or port number represented as a string.

What happens if the getaddrinforequest for IPv6 addresses fails?

If the getaddrinforequest for IPv6 addresses fails, a name service request is made for IPv4 addresses and these addresses are converted to IPv4-mapped IPv6 address format. This option is supported on Windows Vista and later.

Posted in General