The old code uses errno as the primary indicator for success or
failure. This is wrong because errno is only set for specific
combinations of the status return value and the h_errno variable.
(cherry picked from commit f4a6be2582)
A dot-less host name without an /etc/resolv.conf file caused an
assertion failure in update_from_conf because the function would not
deal correctly with the empty search list case.
Thanks to Andreas Schwab for debugging assistence.
This commit enhances the stub resolver to reload the configuration
in the per-thread _res object if the /etc/resolv.conf file has
changed. The resolver checks whether the application has modified
_res and will not overwrite the _res object in that case.
The struct resolv_context mechanism is used to check the
configuration file only once per name lookup.
This commit adds the remaining unchanging members (which are loaded
from /etc/resolv.conf) to struct resolv_conf.
The extended name server list is currently not used by the stub
resolver. The switch depends on a cleanup: The _u._ext.nssocks
array stores just a single socket, and needs to be replaced with
a single socket value.
(The compatibility gethostname implementation does not use the
extended addres sort list, either. Updating the compat code is
not worthwhile.)
This change uses the extended resolver state in struct resolv_conf to
store the search list. If applications have not patched the _res
object directly, this extended search list will be used by the stub
resolver during name resolution.
This change provides additional resolver configuration state which
is not exposed through the _res ABI. It reuses the existing
initstamp field in the supposedly-private part of _res. Some effort
is undertaken to avoid memory safety issues introduced by applications
which directly patch the _res object.
With this commit, only the initstamp field is moved into struct
resolv_conf. Additional members will be added later, eventually
migrating the entire resolver configuration.
struct resolv_context objects provide a temporary resolver context
which does not change during a name lookup operation. Only when the
outmost context is created, the stub resolver configuration is
verified to be current (at present, only against previous res_init
calls). Subsequent attempts to obtain the context will reuse the
result of the initial verification operation.
struct resolv_context can also be extended in the future to store
data which needs to be deallocated during thread cancellation.
Some Linux kernels have very aggressive ICMP rate limiting on the
loopback interface. This commit introduces a minimal echoing DNS server
inside the network namespace, so that there is no need for ICMP error
messages anymore.
Many callers of __res_maybe_init also call _res_hconf_init.
Additional calls to the latter do not hurt because the function
does its work only once. (/etc/hosts.conf is not reloaded or
even checked for changes.) This means that we can simplify the
code by calling _res_hconf_init directly from __res_vinit.
Every file that uses libc_hidden_nolink_sunrpc or
libnsl_hidden_nolink_def needs to include shlib-compat.h. Currently,
most of them are getting it via stdio.h, because libio.h refers to
SHLIB_COMPAT when _LIBC is defined, so it includes shlib-compat.h. My
experimental patch to not install libio.h breaks that chain; stdio.h
no longer pulls in libio.h even for internal users.
Accordingly, this patch adds #include <shlib-compat.h> to many files
in sunrpc/ and nis/. There are also a small number of really obvious
fixups to includes that caught my eye while proofreading the patch -
not including headers twice in a row, not worrying about portability
to Ultrix anymore, sort of thing.
* nis/nis_add.c, nis/nis_addmember.c, nis/nis_call.c
* nis/nis_checkpoint.c, nis/nis_clone_dir.c, nis/nis_clone_obj.c
* nis/nis_clone_res.c, nis/nis_creategroup.c, nis/nis_defaults.c
* nis/nis_destroygroup.c, nis/nis_domain_of.c
* nis/nis_domain_of_r.c, nis/nis_error.c, nis/nis_file.c
* nis/nis_free.c, nis/nis_getservlist.c, nis/nis_ismember.c
* nis/nis_local_names.c, nis/nis_lookup.c, nis/nis_mkdir.c
* nis/nis_modify.c, nis/nis_ping.c, nis/nis_print.c
* nis/nis_print_group_entry.c, nis/nis_remove.c
* nis/nis_removemember.c, nis/nis_rmdir.c, nis/nis_server.c
* nis/nis_subr.c, nis/nis_table.c, nis/nis_util.c
* nis/nis_verifygroup.c, nis/nis_xdr.c, nis/yp_xdr.c
* nis/ypclnt.c, nis/ypupdate_xdr.c, sunrpc/auth_des.c
* sunrpc/auth_none.c, sunrpc/auth_unix.c, sunrpc/authdes_prot.c
* sunrpc/authuxprot.c, sunrpc/clnt_gen.c, sunrpc/clnt_perr.c
* sunrpc/clnt_raw.c, sunrpc/clnt_simp.c, sunrpc/clnt_tcp.c
* sunrpc/clnt_udp.c, sunrpc/clnt_unix.c, sunrpc/des_crypt.c
* sunrpc/des_soft.c, sunrpc/get_myaddr.c, sunrpc/key_call.c
* sunrpc/key_prot.c, sunrpc/netname.c, sunrpc/pm_getmaps.c
* sunrpc/pm_getport.c, sunrpc/pmap_clnt.c, sunrpc/pmap_prot.c
* sunrpc/pmap_prot2.c, sunrpc/pmap_rmt.c, sunrpc/publickey.c
* sunrpc/rpc_cmsg.c, sunrpc/rpc_dtable.c, sunrpc/rpc_prot.c
* sunrpc/rpc_thread.c, sunrpc/rtime.c, sunrpc/svc.c
* sunrpc/svc_auth.c, sunrpc/svc_raw.c, sunrpc/svc_run.c
* sunrpc/svc_tcp.c, sunrpc/svc_udp.c, sunrpc/svc_unix.c
* sunrpc/svcauth_des.c, sunrpc/xdr.c, sunrpc/xdr_array.c
* sunrpc/xdr_float.c, sunrpc/xdr_intXX_t.c, sunrpc/xdr_mem.c
* sunrpc/xdr_rec.c, sunrpc/xdr_ref.c, sunrpc/xdr_sizeof.c
* sunrpc/xdr_stdio.c: Include shlib-compat.h.
* sunrpc/des_crypt.c, sunrpc/des_soft.c: No need to include
abi-versions.h as well as shlib-compat.h.
* sunrpc/get_myaddr.c: Remove obsolete comment.
* sunrpc/pmap_rmt.c: Remove obsolete comment and #undef.
* sunrpc/rpc_thread.c: Include libc-lock.h only once.
* resolv/res_libc.c: Include shlib-compat.h only once.
