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nm-daemon-helper: implement 'resolve-address' operation

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Implement a new operation to resolve the hostname from an
address. Note the call to __nss_configure_lookup("hosts", "dns"): this
configures the glibc Name Service Switch (NSS) to only use DNS,
bypassing other modules that might be configured in
/etc/nsswitch.conf. Other modules like 'myhostname' or 'resolve' can
return synthesized names, while we are only interested in real DNS
results.

(cherry picked from commit 648b0848f1)
This commit is contained in:
Beniamino Galvani 2021-05-25 09:38:27 +02:00
parent 00126e57b4
commit ffd6c5e3f4
1 changed files with 51 additions and 2 deletions
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53
src/nm-daemon-helper/nm-daemon-helper.c
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@ -4,6 +4,9 @@
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <nss.h>
#include "libnm-std-aux/nm-std-aux.h"
@ -46,6 +49,51 @@ cmd_version(void)
return RETURN_SUCCESS;
}
static int
cmd_resolve_address(void)
{
nm_auto_free char *address = NULL;
union {
struct sockaddr_in in;
struct sockaddr_in6 in6;
} sockaddr;
socklen_t sockaddr_size;
char name[NI_MAXHOST];
address = read_arg();
if (!address)
return RETURN_INVALID_ARGS;
if (more_args())
return RETURN_INVALID_ARGS;
memset(&sockaddr, 0, sizeof(sockaddr));
__nss_configure_lookup("hosts", "dns");
if (inet_pton(AF_INET, address, &sockaddr.in.sin_addr) == 1) {
sockaddr.in.sin_family = AF_INET;
sockaddr_size = sizeof(struct sockaddr_in);
} else if (inet_pton(AF_INET6, address, &sockaddr.in6.sin6_addr) == 1) {
sockaddr.in6.sin6_family = AF_INET6;
sockaddr_size = sizeof(struct sockaddr_in6);
} else
return RETURN_INVALID_ARGS;
if (getnameinfo((struct sockaddr *) &sockaddr,
sockaddr_size,
name,
sizeof(name),
NULL,
0,
NI_NAMEREQD)
!= 0)
return RETURN_ERROR;
printf("%s", name);
return RETURN_SUCCESS;
}
int
main(int argc, char **argv)
{
@ -55,9 +103,10 @@ main(int argc, char **argv)
if (!cmd)
return RETURN_INVALID_CMD;
if (nm_streq(cmd, "version")) {
if (nm_streq(cmd, "version"))
return cmd_version();
}
if (nm_streq(cmd, "resolve-address"))
return cmd_resolve_address();
return RETURN_INVALID_CMD;
}