1ARES_SET_SOCKET_FUNCTIONS(3)Library Functions ManualARES_SET_SOCKET_FUNCTIONS(3)
2
6 ares_set_socket_functions - Set socket io callbacks
7
9 #include <ares.h>
10 struct ares_socket_functions {
12 ares_socket_t(*asocket)(int, int, int, void *);
13 int(*aclose)(ares_socket_t, void *);
14 int(*aconnect)(ares_socket_t, const struct sockaddr *, ares_socklen_t, void *);
15 ares_ssize_t(*arecvfrom)(ares_socket_t, void *, size_t, int, struct sockaddr *, ares_socklen_t *, void *);
16 ares_ssize_t(*asendv)(ares_socket_t, const struct iovec *, int, void *);
17 };
18 void ares_set_socket_functions(ares_channel channel,
21 const struct ares_socket_functions * functions,
22 void *user_data);
23
26 This function sets a set of callback functions in the given ares chan‐
27 nel handle. These callback functions will be invoked to create/destroy
28 socket objects and perform io, instead of the normal system calls. A
29 client application can override normal network operation fully through
30 this functionality, and provide its own transport layer.
31 All callback functions are expected to operate like their system equiv‐
33 alents, and to set errno(3) to an appropriate error code on failure. C-
34 ares also expects all io functions to behave asynchronously, i.e. as if
35 the socket object has been set to non-blocking mode. Thus read/write
36 calls (for TCP connections) are expected to often generate EAGAIN or
37 EWOULDBLOCK.
38 The user_data value is provided to each callback function invocation to
41 serve as context.
42 The ares_socket_functions must provide the following callbacks:
44 asocket ares_socket_t(*)(int domain, int type, int protocol,
46 void * user_data)
47 Creates an endpoint for communication and returns a
48 descriptor. domain, type, and protocol each corre‐
49 spond to the parameters of socket(2). Returns ahan‐
50 dle to the newly created socket, or -1 on error.
51 aclose int(*)(ares_socket_t fd, void * user_data)
53 Closes the socket endpoint indicated by fd. See
54 close(2)
55 aconnect int(*)(ares_socket_t fd, const struct sockaddr *
57 addr, ares_socklen_t addr_len, void * user_data)
58 Initiate a connection to the address indicated by
59 addr on a socket. See connect(2)
60 arecvfrom ares_ssize_t(*)(ares_socket_t fd, void * buffer,
63 size_t buf_size, int flags, struct sockaddr * addr,
64 ares_socklen_t * addr_len, void * user_data)
65 Receives data from remote socket endpoint, if avail‐
66 able. If the addr parameter is not NULL and the con‐
67 nection protocol provides the source address, the
68 callback should fill this in. See recvfrom(2)
69 asendv ares_ssize_t(*)(ares_socket_t fd, const struct iovec
72 * data, int len, void * user_data)
73 Send data, as provided by the iovec array data, to
74 the socket endpoint. See writev(2),
75 The ares_socket_functions struct provided is not copied but directly
78 referenced, and must thus remain valid through out the channels and any
79 created socket's lifetime.
80
82 Added in c-ares 1.13.0
83
85 ares_init_options(3), socket(2), close(2), connect(2), recv(2),
86 recvfrom(2), send(2), writev(2)
87
89 Carl Wilund
90 13 Dec 2016 ARES_SET_SOCKET_FUNCTIONS(3)