mirror of
https://git.busybox.net/busybox.git
synced 2024-12-01 01:23:32 +08:00
224 lines
9.3 KiB
Plaintext
224 lines
9.3 KiB
Plaintext
We need better network address conv helpers.
|
|
This is what our applets want:
|
|
|
|
sockaddr -> hostname
|
|
udhcp: hostname -> ipv4 addr
|
|
nslookup: hostname -> list of names - done
|
|
tftp: host,port -> sockaddr
|
|
nc: host,port -> sockaddr
|
|
inetd: ?
|
|
traceroute: ?, hostname -> ipv4 addr
|
|
arping hostname -> ipv4 addr
|
|
ping6 hostname -> ipv6 addr
|
|
ifconfig hostname -> ipv4 addr (FIXME error check?)
|
|
ipcalc ipv4 addr -> hostname
|
|
syslogd hostname -> sockaddr
|
|
inet_common.c: buggy. hostname -> ipv4 addr
|
|
mount hostname -> sockaddr_in
|
|
|
|
==================
|
|
HOWTO get rid of inet_ntoa/aton:
|
|
|
|
foo.sin_addr.s_addr = inet_addr(cp);
|
|
-
|
|
inet_pton(AF_INET, cp, &foo.sin_addr);
|
|
|
|
inet_aton(cp, &foo.sin_addr);
|
|
-
|
|
inet_pton(AF_INET, cp, &foo.sin_addr);
|
|
|
|
ptr = inet_ntoa(foo.sin_addr);
|
|
-
|
|
char str[INET_ADDRSTRLEN];
|
|
ptr = inet_ntop(AF_INET, &foo.sin_addr, str, sizeof(str));
|
|
|
|
===================
|
|
|
|
struct addrinfo {
|
|
int ai_flags;
|
|
int ai_family;
|
|
int ai_socktype;
|
|
int ai_protocol;
|
|
size_t ai_addrlen;
|
|
struct sockaddr *ai_addr;
|
|
char *ai_canonname;
|
|
struct addrinfo *ai_next;
|
|
};
|
|
int getaddrinfo(const char *node, const char *service,
|
|
const struct addrinfo *hints,
|
|
struct addrinfo **res);
|
|
|
|
void freeaddrinfo(struct addrinfo *res);
|
|
|
|
const char *gai_strerror(int errcode);
|
|
|
|
The members ai_family, ai_socktype, and ai_protocol have the same meaning
|
|
as the corresponding parameters in the socket(2) system call. The getad-
|
|
drinfo(3) function returns socket addresses in either IPv4 or IPv6 address
|
|
family, (ai_family will be set to either AF_INET or AF_INET6).
|
|
|
|
The hints parameter specifies the preferred socket type, or protocol. A
|
|
NULL hints specifies that any network address or protocol is acceptable.
|
|
If this parameter is not NULL it points to an addrinfo structure whose
|
|
ai_family, ai_socktype, and ai_protocol members specify the preferred
|
|
socket type. AF_UNSPEC in ai_family specifies any protocol family (either
|
|
IPv4 or IPv6, for example). 0 in ai_socktype or ai_protocol specifies
|
|
that any socket type or protocol is acceptable as well. The ai_flags mem-
|
|
ber specifies additional options, defined below. Multiple flags are spec-
|
|
ified by logically OR-ing them together. All the other members in the
|
|
hints parameter must contain either 0, or a null pointer.
|
|
|
|
The node or service parameter, but not both, may be NULL. node specifies
|
|
either a numerical network address (dotted-decimal format for IPv4, hex-
|
|
adecimal format for IPv6) or a network hostname, whose network addresses
|
|
are looked up and resolved. If hints.ai_flags contains the AI_NUMERICHOST
|
|
flag then the node parameter must be a numerical network address. The
|
|
AI_NUMERICHOST flag suppresses any potentially lengthy network host
|
|
address lookups.
|
|
|
|
The getaddrinfo(3) function creates a linked list of addrinfo structures,
|
|
one for each network address subject to any restrictions imposed by the
|
|
hints parameter. The ai_canonname field of the first of these addrinfo
|
|
structures is set to point to the official name of the host, if
|
|
hints.ai_flags includes the AI_CANONNAME flag. ai_family, ai_socktype,
|
|
and ai_protocol specify the socket creation parameters. A pointer to the
|
|
socket address is placed in the ai_addr member, and the length of the
|
|
socket address, in bytes, is placed in the ai_addrlen member.
|
|
|
|
If node is NULL, the network address in each socket structure is initial-
|
|
ized according to the AI_PASSIVE flag, which is set in hints.ai_flags.
|
|
The network address in each socket structure will be left unspecified if
|
|
AI_PASSIVE flag is set. This is used by server applications, which intend
|
|
to accept client connections on any network address. The network address
|
|
will be set to the loopback interface address if the AI_PASSIVE flag is
|
|
not set. This is used by client applications, which intend to connect to
|
|
a server running on the same network host.
|
|
|
|
If hints.ai_flags includes the AI_ADDRCONFIG flag, then IPv4 addresses are
|
|
returned in the list pointed to by result only if the local system has at
|
|
least has at least one IPv4 address configured, and IPv6 addresses are
|
|
only returned if the local system has at least one IPv6 address config-
|
|
ured.
|
|
|
|
If hint.ai_flags specifies the AI_V4MAPPED flag, and hints.ai_family was
|
|
specified as AF_INET6, and no matching IPv6 addresses could be found, then
|
|
return IPv4-mapped IPv6 addresses in the list pointed to by result. If
|
|
both AI_V4MAPPED and AI_ALL are specified in hints.ai_family, then return
|
|
both IPv6 and IPv4-mapped IPv6 addresses in the list pointed to by result.
|
|
AI_ALL is ignored if AI_V4MAPPED is not also specified.
|
|
|
|
service sets the port number in the network address of each socket struc-
|
|
ture. If service is NULL the port number will be left uninitialized. If
|
|
AI_NUMERICSERV is specified in hints.ai_flags and service is not NULL,
|
|
then service must point to a string containing a numeric port number.
|
|
This flag is used to inhibit the invocation of a name resolution service
|
|
in cases where it is known not to be required.
|
|
|
|
|
|
==============
|
|
|
|
int getnameinfo(const struct sockaddr *sa, socklen_t salen,
|
|
char *host, size_t hostlen,
|
|
char *serv, size_t servlen, int flags);
|
|
|
|
The getnameinfo(3) function is defined for protocol-independent
|
|
address-to-nodename translation. It combines the functionality
|
|
of gethostbyaddr(3) and getservbyport(3) and is the inverse of
|
|
getaddrinfo(3). The sa argument is a pointer to a generic socket address
|
|
structure (of type sockaddr_in or sockaddr_in6) of size salen that
|
|
holds the input IP address and port number. The arguments host and
|
|
serv are pointers to buffers (of size hostlen and servlen respectively)
|
|
to hold the return values.
|
|
|
|
The caller can specify that no hostname (or no service name) is required
|
|
by providing a NULL host (or serv) argument or a zero hostlen (or servlen)
|
|
parameter. However, at least one of hostname or service name must be requested.
|
|
|
|
The flags argument modifies the behaviour of getnameinfo(3) as follows:
|
|
|
|
NI_NOFQDN
|
|
If set, return only the hostname part of the FQDN for local hosts.
|
|
|
|
NI_NUMERICHOST
|
|
If set, then the numeric form of the hostname is returned.
|
|
(When not set, this will still happen in case the node's name
|
|
cannot be looked up.)
|
|
|
|
NI_NAMEREQD
|
|
If set, then a error is returned if the hostname cannot be looked up.
|
|
|
|
NI_NUMERICSERV
|
|
If set, then the service address is returned in numeric form,
|
|
for example by its port number.
|
|
|
|
NI_DGRAM
|
|
If set, then the service is datagram (UDP) based rather than stream
|
|
(TCP) based. This is required for the few ports (512-514) that have different
|
|
services for UDP and TCP.
|
|
|
|
=================
|
|
|
|
Modified IPv6-aware C code:
|
|
|
|
struct addrinfo *res, *aip;
|
|
struct addrinfo hints;
|
|
int sock = -1;
|
|
int error;
|
|
|
|
/* Get host address. Any type of address will do. */
|
|
memset(&hints, 0, sizeof(hints));
|
|
hints.ai_flags = AI_ALL|AI_ADDRCONFIG;
|
|
hints.ai_socktype = SOCK_STREAM;
|
|
|
|
error = getaddrinfo(hostname, servicename, &hints, &res);
|
|
if (error != 0) {
|
|
(void) fprintf(stderr,
|
|
"getaddrinfo: %s for host %s service %s\n",
|
|
gai_strerror(error), hostname, servicename);
|
|
return -1;
|
|
}
|
|
/* Try all returned addresses until one works */
|
|
for (aip = res; aip != NULL; aip = aip->ai_next) {
|
|
/*
|
|
* Open socket. The address type depends on what
|
|
* getaddrinfo() gave us.
|
|
*/
|
|
sock = socket(aip->ai_family, aip->ai_socktype, aip->ai_protocol);
|
|
if (sock == -1) {
|
|
perror("socket");
|
|
freeaddrinfo(res);
|
|
return -1;
|
|
}
|
|
|
|
/* Connect to the host. */
|
|
if (connect(sock, aip->ai_addr, aip->ai_addrlen) == -1) {
|
|
perror("connect");
|
|
(void) close(sock);
|
|
sock = -1;
|
|
continue;
|
|
}
|
|
break;
|
|
}
|
|
freeaddrinfo(res);
|
|
|
|
Note that for new applications, if you write address-family-agnostic data structures,
|
|
there is no need for porting.
|
|
|
|
However, when it comes to server-side programming in C/C++, there is an additional wrinkle.
|
|
Namely, depending on whether your application is written for a dual-stack platform, such
|
|
as Solaris or Linux, or a single-stack platform, such as Windows, you would need to
|
|
structure the code differently.
|
|
|
|
Here's the corresponding server C code for a dual-stack platform:
|
|
|
|
int ServSock, csock;
|
|
/* struct sockaddr is too small! */
|
|
struct sockaddr_storage addr, from;
|
|
...
|
|
ServSock = socket(AF_INET6, SOCK_STREAM, PF_INET6);
|
|
bind(ServSock, &addr, sizeof(addr));
|
|
do {
|
|
csock = accept(ServSocket, &from, sizeof(from));
|
|
doClientStuff(csock);
|
|
} while (!finished);
|