From 344874fcd0a3fc1f9bc6cdf34ecaf537c10a3ad3 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Mon, 24 Oct 2016 18:50:43 +0200 Subject: nss-resolve: be a bit more careful with returning NSS_STATUS_NOTFOUND Let's tighten the cases when our module returns NSS_STATUS_NOTFOUND. Let's do so only if we actually managed to talk to resolved. In all other cases stick to NSS_STATUS_UNAVAIL as before, as it clearly indicates that our module or the system is borked, and the "dns" fallback should really take place. In particular this fixes the 2nd-level fallback from our own dlopen() based fallback handling. In this case we really should return UNAVAIL so that the caller can apply its own fallback still. Fix-up for d7247512a904f1dd74125859d8da66166c2a6933. Note that our own dlopen() based fallback is pretty much redundant now if nsswitch.conf is configured like this: hosts: files mymachines resolve [!UNAVAIL=return] dns myhostname In a future release we should probably drop our internal fallback then, in favour of this nsswitch.conf-based one. --- src/nss-resolve/nss-resolve.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'src/nss-resolve/nss-resolve.c') diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c index eea91e3e88..d46a3afe91 100644 --- a/src/nss-resolve/nss-resolve.c +++ b/src/nss-resolve/nss-resolve.c @@ -121,6 +121,7 @@ enum nss_status _nss_resolve_gethostbyname4_r( _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; struct gaih_addrtuple *r_tuple, *r_tuple_first = NULL; _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + enum nss_status ret = NSS_STATUS_UNAVAIL; const char *canonical = NULL; size_t l, ms, idx; char *r_name; @@ -167,6 +168,10 @@ enum nss_status _nss_resolve_gethostbyname4_r( if (bus_error_shall_fallback(&error)) goto fallback; + /* Treat all other error conditions as NOTFOUND, and fail. This includes DNSSEC errors and + suchlike. (We don't use UNAVAIL in this case so that the nsswitch.conf configuration can distuingish + such executed but negative replies from complete failure to talk to resolved. */ + ret = NSS_STATUS_NOTFOUND; goto fail; } @@ -279,12 +284,9 @@ fallback: } fail: - /* When we arrive here, resolved runs and has answered (fallback to - * "dns" is handled earlier). So we have a definitive "no" answer and - * should not fall back to subsequent NSS modules via "UNAVAIL". */ *errnop = -r; *h_errnop = NO_RECOVERY; - return NSS_STATUS_NOTFOUND; + return ret; } enum nss_status _nss_resolve_gethostbyname3_r( @@ -300,6 +302,7 @@ enum nss_status _nss_resolve_gethostbyname3_r( _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; char *r_name, *r_aliases, *r_addr, *r_addr_list; _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + enum nss_status ret = NSS_STATUS_UNAVAIL; size_t l, idx, ms, alen; const char *canonical; int c, r, i = 0; @@ -353,6 +356,7 @@ enum nss_status _nss_resolve_gethostbyname3_r( if (bus_error_shall_fallback(&error)) goto fallback; + ret = NSS_STATUS_NOTFOUND; goto fail; } @@ -479,7 +483,7 @@ fallback: fail: *errnop = -r; *h_errnop = NO_RECOVERY; - return NSS_STATUS_NOTFOUND; + return ret; } enum nss_status _nss_resolve_gethostbyaddr2_r( @@ -494,6 +498,7 @@ enum nss_status _nss_resolve_gethostbyaddr2_r( _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; char *r_name, *r_aliases, *r_addr, *r_addr_list; _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + enum nss_status ret = NSS_STATUS_UNAVAIL; unsigned c = 0, i = 0; size_t ms = 0, idx; const char *n; @@ -560,7 +565,7 @@ enum nss_status _nss_resolve_gethostbyaddr2_r( if (bus_error_shall_fallback(&error)) goto fallback; - + ret = NSS_STATUS_NOTFOUND; goto fail; } @@ -669,7 +674,7 @@ fallback: fail: *errnop = -r; *h_errnop = NO_RECOVERY; - return NSS_STATUS_NOTFOUND; + return ret; } NSS_GETHOSTBYNAME_FALLBACKS(resolve); -- cgit v1.2.3-54-g00ecf