Cryptography and SSL/TLS Toolkit



BIO_lookup_type, BIO_ADDRINFO, BIO_ADDRINFO_next, BIO_ADDRINFO_free, BIO_ADDRINFO_family, BIO_ADDRINFO_socktype, BIO_ADDRINFO_protocol, BIO_ADDRINFO_address, BIO_lookup_ex, BIO_lookup - BIO_ADDRINFO type and routines


#include <sys/types.h>
#include <openssl/bio.h>

typedef union bio_addrinfo_st BIO_ADDRINFO;

enum BIO_lookup_type {

int BIO_lookup_ex(const char *host, const char *service, int lookup_type,
                  int family, int socktype, int protocol, BIO_ADDRINFO **res);
int BIO_lookup(const char *host, const char *service,
               enum BIO_lookup_type lookup_type,
               int family, int socktype, BIO_ADDRINFO **res);

int BIO_ADDRINFO_family(const BIO_ADDRINFO *bai);
int BIO_ADDRINFO_socktype(const BIO_ADDRINFO *bai);
int BIO_ADDRINFO_protocol(const BIO_ADDRINFO *bai);
const BIO_ADDR *BIO_ADDRINFO_address(const BIO_ADDRINFO *bai);


The BIO_ADDRINFO type is a wrapper for address information types provided on your platform.

BIO_ADDRINFO normally forms a chain of several that can be picked at one by one.

BIO_lookup_ex() looks up a specified host and service, and uses lookup_type to determine what the default address should be if host is NULL. family, socktype and protocol are used to determine what protocol family, socket type and protocol should be used for the lookup. family can be any of AF_INET, AF_INET6, AF_UNIX and AF_UNSPEC. socktype can be SOCK_STREAM, SOCK_DGRAM or 0. Specifying 0 indicates that any type can be used. protocol specifies a protocol such as IPPROTO_TCP, IPPROTO_UDP or IPPORTO_SCTP. If set to 0 than any protocol can be used. res points at a pointer to hold the start of a BIO_ADDRINFO chain.

For the family AF_UNIX, BIO_lookup_ex() will ignore the service parameter and expects the host parameter to hold the path to the socket file.

BIO_lookup() does the same as BIO_lookup_ex() but does not provide the ability to select based on the protocol (any protocol may be returned).

BIO_ADDRINFO_family() returns the family of the given BIO_ADDRINFO. The result will be one of the constants AF_INET, AF_INET6 and AF_UNIX.

BIO_ADDRINFO_socktype() returns the socket type of the given BIO_ADDRINFO. The result will be one of the constants SOCK_STREAM and SOCK_DGRAM.

BIO_ADDRINFO_protocol() returns the protocol id of the given BIO_ADDRINFO. The result will be one of the constants IPPROTO_TCP and IPPROTO_UDP.

BIO_ADDRINFO_address() returns the underlying BIO_ADDR of the given BIO_ADDRINFO.

BIO_ADDRINFO_next() returns the next BIO_ADDRINFO in the chain from the given one.

BIO_ADDRINFO_free() frees the chain of BIO_ADDRINFO starting with the given one. If the argument is NULL, nothing is done.


BIO_lookup_ex() and BIO_lookup() return 1 on success and 0 when an error occurred, and will leave an error indication on the OpenSSL error stack in that case.

All other functions described here return 0 or NULL when the information they should return isn't available.


The BIO_lookup_ex() implementation uses the platform provided getaddrinfo() function. On Linux it is known that specifying 0 for the protocol will not return any SCTP based addresses when calling getaddrinfo(). Therefore, if an SCTP address is required then the protocol parameter to BIO_lookup_ex() should be explicitly set to IPPROTO_SCTP. The same may be true on other platforms.


The BIO_lookup_ex() function was added in OpenSSL 1.1.1.

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Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at