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Add dns_resolver option

Browse source 
This allows one to configure the address of the DNS server to use for
lookup operations.

Addresses GH-216
This commit is contained in:
Jon Siwek 2018-11-21 13:42:25 -06:00
parent fd63168171
commit af82e87699
4 changed files with 121 additions and 23 deletions
Download patch file Download diff file Expand all files Collapse all files

96
src/nb_dns.c
View file

@ -86,7 +86,7 @@ struct nb_dns_hostent {
struct nb_dns_info {
int s; /* Resolver file descriptor */
struct sockaddr_in server; /* server address to bind to */
struct sockaddr_storage server; /* server address to bind to */
struct nb_dns_entry *list; /* outstanding requests */
struct nb_dns_hostent dns_hostent;
};
@ -109,6 +109,18 @@ my_strerror(int errnum)
#endif
}
static const char* sa_ntop(struct sockaddr* sa, char* buf, int len)
{
if ( sa->sa_family == AF_INET )
return inet_ntop(sa->sa_family,
&(((struct sockaddr_in*)sa)->sin_addr),
buf, len);
else
return inet_ntop(sa->sa_family,
&(((struct sockaddr_in6*)sa)->sin6_addr),
buf, len);
}
struct nb_dns_info *
nb_dns_init(char *errstr)
{
@ -136,13 +148,12 @@ nb_dns_init(char *errstr)
for ( i = 0; i < _res.nscount; ++i )
{
nd->server = _res.nsaddr_list[i];
memcpy(&nd->server, &_res.nsaddr_list[i], sizeof(struct sockaddr_in));
/* XXX support IPv6 */
if ( nd->server.sin_family != AF_INET )
if ( nd->server.ss_family != AF_INET )
continue;
nd->s = socket(nd->server.sin_family, SOCK_DGRAM, 0);
nd->s = socket(nd->server.ss_family, SOCK_DGRAM, 0);
if ( nd->s < 0 )
{
@ -153,10 +164,14 @@ nb_dns_init(char *errstr)
}
if ( connect(nd->s, (struct sockaddr *)&nd->server,
sizeof(struct sockaddr)) < 0 )
nd->server.ss_family == AF_INET ?
sizeof(struct sockaddr_in) :
sizeof(struct sockaddr_in6)) < 0 )
{
snprintf(errstr, NB_DNS_ERRSIZE, "connect(%s): %s",
inet_ntoa(nd->server.sin_addr), my_strerror(errno));
char s[INET6_ADDRSTRLEN];
sa_ntop((struct sockaddr*)&nd->server, s, INET6_ADDRSTRLEN);
snprintf(errstr, NB_DNS_ERRSIZE, "connect(%s): %s", s,
my_strerror(errno));
close(nd->s);
free(nd);
return (NULL);
@ -170,6 +185,58 @@ nb_dns_init(char *errstr)
return (NULL);
}
struct nb_dns_info *
nb_dns_init2(char *errstr, struct sockaddr* sa)
{
register struct nb_dns_info *nd;
nd = (struct nb_dns_info *)malloc(sizeof(*nd));
if (nd == NULL) {
snprintf(errstr, NB_DNS_ERRSIZE, "nb_dns_init: malloc(): %s",
my_strerror(errno));
return (NULL);
}
memset(nd, 0, sizeof(*nd));
nd->s = -1;
if ( sa->sa_family == AF_INET )
{
memcpy(&nd->server, sa, sizeof(struct sockaddr_in));
((struct sockaddr_in*)&nd->server)->sin_port = htons(53);
}
else
{
memcpy(&nd->server, sa, sizeof(struct sockaddr_in6));
((struct sockaddr_in6*)&nd->server)->sin6_port = htons(53);
}
nd->s = socket(nd->server.ss_family, SOCK_DGRAM, 0);
if ( nd->s < 0 )
{
snprintf(errstr, NB_DNS_ERRSIZE, "socket(): %s",
my_strerror(errno));
free(nd);
return (NULL);
}
if ( connect(nd->s, (struct sockaddr *)&nd->server,
nd->server.ss_family == AF_INET ?
sizeof(struct sockaddr_in) :
sizeof(struct sockaddr_in6)) < 0 )
{
char s[INET6_ADDRSTRLEN];
sa_ntop((struct sockaddr*)&nd->server, s, INET6_ADDRSTRLEN);
snprintf(errstr, NB_DNS_ERRSIZE, "connect(%s): %s", s,
my_strerror(errno));
close(nd->s);
free(nd);
return (NULL);
}
return (nd);
}
void
nb_dns_finish(struct nb_dns_info *nd)
{
@ -226,12 +293,12 @@ _nb_dns_cmpsockaddr(register struct sockaddr *sa1,
sin6a = (struct sockaddr_in6 *)sa1;
sin6b = (struct sockaddr_in6 *)sa2;
if (sin6a->sin6_port != sin6b->sin6_port) {
snprintf(errstr, NB_DNS_ERRSIZE, serr, 2);
snprintf(errstr, NB_DNS_ERRSIZE, serr, 62);
return (-1);
}
if (memcmp(&sin6a->sin6_addr, &sin6b->sin6_addr,
sizeof(sin6a->sin6_addr)) != 0) {
snprintf(errstr, NB_DNS_ERRSIZE, serr, 3);
snprintf(errstr, NB_DNS_ERRSIZE, serr, 63);
return (-1);
}
break;
@ -446,7 +513,7 @@ nb_dns_activity(struct nb_dns_info *nd, struct nb_dns_result *nr, char *errstr)
register int msglen, qtype, atype, n, i;
register struct nb_dns_entry *ne, *lastne;
socklen_t fromlen;
struct sockaddr from;
struct sockaddr_storage from;
u_long msg[MAXPACKET / sizeof(u_long)];
register char *bp, *ep;
register char **ap, **hap;
@ -460,7 +527,8 @@ nb_dns_activity(struct nb_dns_info *nd, struct nb_dns_result *nr, char *errstr)
/* This comes from the second half of do_query() */
fromlen = sizeof(from);
msglen = recvfrom(nd->s, (char *)msg, sizeof(msg), 0, &from, &fromlen);
msglen = recvfrom(nd->s, (char *)msg, sizeof(msg), 0,
(struct sockaddr*)&from, &fromlen);
if (msglen <= 0) {
snprintf(errstr, NB_DNS_ERRSIZE, "recvfrom(): %s",
my_strerror(errno));
@ -479,8 +547,8 @@ nb_dns_activity(struct nb_dns_info *nd, struct nb_dns_result *nr, char *errstr)
}
/* RES_INSECURE1 style check */
if (_nb_dns_cmpsockaddr((struct sockaddr *)&nd->server, &from,
errstr) < 0) {
if (_nb_dns_cmpsockaddr((struct sockaddr*)&nd->server,
(struct sockaddr*)&from, errstr) < 0) {
nr->host_errno = NO_RECOVERY;
return (-1);
}