diff options
author | Lennart Poettering <lennart@poettering.net> | 2021-11-22 15:17:34 +0100 |
---|---|---|
committer | Lennart Poettering <lennart@poettering.net> | 2021-11-22 22:33:40 +0100 |
commit | ae78529fc75027b3487b64e0d22a572fd9c8ffeb (patch) | |
tree | 6d28e30bee8904b5656cfc343bf7d0116cdd7015 /src/nss-resolve/nss-resolve.c | |
parent | resolved: fix ResolveService() hostname handling (diff) | |
download | systemd-ae78529fc75027b3487b64e0d22a572fd9c8ffeb.tar.xz systemd-ae78529fc75027b3487b64e0d22a572fd9c8ffeb.zip |
resolved: properly signal transient errors back to NSS stack
NSS mostly knows four error cases: SUCCESS, NOTFOUND, UNAVAIL, TRYAGAIN,
and they can all be used in nsswitch.conf to route requests.
So far nss-resolve would return SUCCESS + NOTFOUND + UNAVAIL. Let's also
return TRYAGAIN in some cases, specifically the ones where we are
currntly unable to resolve a request but likely could later. i.e.
errors caused by networking issues or such.
Fixes: #20786
Diffstat (limited to 'src/nss-resolve/nss-resolve.c')
-rw-r--r-- | src/nss-resolve/nss-resolve.c | 55 |
1 files changed, 46 insertions, 9 deletions
diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c index d77ffdd9f2..951d141f35 100644 --- a/src/nss-resolve/nss-resolve.c +++ b/src/nss-resolve/nss-resolve.c @@ -41,6 +41,9 @@ NSS_GETHOSTBYNAME_PROTOTYPES(resolve); NSS_GETHOSTBYADDR_PROTOTYPES(resolve); static bool error_shall_fallback(const char *error_id) { + /* The Varlink errors where we shall signal "please fallback" back to the NSS stack, so that some + * fallback module can be loaded. (These are mostly all Varlink-internal errors, as apparently we + * then were unable to even do IPC with systemd-resolved.) */ return STR_IN_SET(error_id, VARLINK_ERROR_DISCONNECTED, VARLINK_ERROR_TIMEOUT, @@ -50,6 +53,16 @@ static bool error_shall_fallback(const char *error_id) { VARLINK_ERROR_METHOD_NOT_IMPLEMENTED); } +static bool error_shall_try_again(const char *error_id) { + /* The Varlink errors where we shall signal "can't answer now but might be able to later" back to the + * NSS stack. These are all errors that indicate lack of configuration or network problems. */ + return STR_IN_SET(error_id, + "io.systemd.Resolve.NoNameServers", + "io.systemd.Resolve.QueryTimedOut", + "io.systemd.Resolve.MaxAttemptsReached", + "io.systemd.Resolve.NetworkDown"); +} + static int connect_to_resolved(Varlink **ret) { _cleanup_(varlink_unrefp) Varlink *link = NULL; int r; @@ -242,9 +255,11 @@ enum nss_status _nss_resolve_gethostbyname4_r( if (r < 0) goto fail; if (!isempty(error_id)) { - if (!error_shall_fallback(error_id)) - goto not_found; - goto fail; + if (error_shall_try_again(error_id)) + goto try_again; + if (error_shall_fallback(error_id)) + goto fail; + goto not_found; } r = json_dispatch(rparams, resolve_hostname_reply_dispatch_table, NULL, json_dispatch_flags, &p); @@ -341,6 +356,12 @@ fail: not_found: *h_errnop = HOST_NOT_FOUND; return NSS_STATUS_NOTFOUND; + +try_again: + UNPROTECT_ERRNO; + *errnop = -r; + *h_errnop = TRY_AGAIN; + return NSS_STATUS_TRYAGAIN; } enum nss_status _nss_resolve_gethostbyname3_r( @@ -390,9 +411,11 @@ enum nss_status _nss_resolve_gethostbyname3_r( if (r < 0) goto fail; if (!isempty(error_id)) { - if (!error_shall_fallback(error_id)) - goto not_found; - goto fail; + if (error_shall_try_again(error_id)) + goto try_again; + if (error_shall_fallback(error_id)) + goto fail; + goto not_found; } r = json_dispatch(rparams, resolve_hostname_reply_dispatch_table, NULL, json_dispatch_flags, &p); @@ -508,6 +531,12 @@ fail: not_found: *h_errnop = HOST_NOT_FOUND; return NSS_STATUS_NOTFOUND; + +try_again: + UNPROTECT_ERRNO; + *errnop = -r; + *h_errnop = TRY_AGAIN; + return NSS_STATUS_TRYAGAIN; } typedef struct ResolveAddressReply { @@ -594,9 +623,11 @@ enum nss_status _nss_resolve_gethostbyaddr2_r( if (r < 0) goto fail; if (!isempty(error_id)) { - if (!error_shall_fallback(error_id)) - goto not_found; - goto fail; + if (error_shall_try_again(error_id)) + goto try_again; + if (error_shall_fallback(error_id)) + goto fail; + goto not_found; } r = json_dispatch(rparams, resolve_address_reply_dispatch_table, NULL, json_dispatch_flags, &p); @@ -694,6 +725,12 @@ fail: not_found: *h_errnop = HOST_NOT_FOUND; return NSS_STATUS_NOTFOUND; + +try_again: + UNPROTECT_ERRNO; + *errnop = -r; + *h_errnop = TRY_AGAIN; + return NSS_STATUS_TRYAGAIN; } NSS_GETHOSTBYNAME_FALLBACKS(resolve); |