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-rw-r--r--src/nss-resolve/nss-resolve.c87
1 files changed, 87 insertions, 0 deletions
diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
index 5268fb763a..b2cb19a7b4 100644
--- a/src/nss-resolve/nss-resolve.c
+++ b/src/nss-resolve/nss-resolve.c
@@ -29,6 +29,7 @@
#include <net/if.h>
#include <stdlib.h>
#include <arpa/inet.h>
+#include <dlfcn.h>
#include "sd-bus.h"
#include "bus-util.h"
@@ -43,6 +44,27 @@ NSS_GETHOSTBYADDR_PROTOTYPES(resolve);
#define DNS_CALL_TIMEOUT_USEC (45*USEC_PER_SEC)
+typedef void (*voidfunc_t)(void);
+
+static voidfunc_t find_fallback(const char *module, const char *symbol) {
+ void *dl;
+
+ /* Try to find a fallback NSS module symbol */
+
+ dl = dlopen(module, RTLD_LAZY|RTLD_NODELETE);
+ if (!dl)
+ return NULL;
+
+ return dlsym(dl, symbol);
+}
+
+static bool bus_error_shall_fallback(sd_bus_error *e) {
+ return sd_bus_error_has_name(e, SD_BUS_ERROR_SERVICE_UNKNOWN) ||
+ sd_bus_error_has_name(e, SD_BUS_ERROR_NAME_HAS_NO_OWNER) ||
+ sd_bus_error_has_name(e, SD_BUS_ERROR_NO_REPLY) ||
+ sd_bus_error_has_name(e, SD_BUS_ERROR_ACCESS_DENIED);
+}
+
static int count_addresses(sd_bus_message *m, int af, const char **canonical) {
int c = 0, r;
@@ -143,6 +165,25 @@ enum nss_status _nss_resolve_gethostbyname4_r(
return NSS_STATUS_NOTFOUND;
}
+ if (bus_error_shall_fallback(&error)) {
+
+ enum nss_status (*fallback)(
+ const char *name,
+ struct gaih_addrtuple **pat,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp);
+
+ fallback = (enum nss_status (*)(const char *name,
+ struct gaih_addrtuple **pat,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp))
+ find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname4_r");
+ if (fallback)
+ return fallback(name, pat, buffer, buflen, errnop, h_errnop, ttlp);
+ }
+
*errnop = -r;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
@@ -309,6 +350,29 @@ enum nss_status _nss_resolve_gethostbyname3_r(
return NSS_STATUS_NOTFOUND;
}
+ if (bus_error_shall_fallback(&error)) {
+
+ enum nss_status (*fallback)(
+ const char *name,
+ int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp,
+ char **canonp);
+
+ fallback = (enum nss_status (*)(const char *name,
+ int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp,
+ char **canonp))
+ find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname3_r");
+ if (fallback)
+ return fallback(name, af, result, buffer, buflen, errnop, h_errnop, ttlp, canonp);
+ }
+
*errnop = -r;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
@@ -505,6 +569,29 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
return NSS_STATUS_NOTFOUND;
}
+ if (bus_error_shall_fallback(&error)) {
+
+ enum nss_status (*fallback)(
+ const void* addr, socklen_t len,
+ int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp);
+
+ fallback = (enum nss_status (*)(
+ const void* addr, socklen_t len,
+ int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp))
+ find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyaddr2_r");
+
+ if (fallback)
+ return fallback(addr, len, af, result, buffer, buflen, errnop, h_errnop, ttlp);
+ }
+
*errnop = -r;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;