/* Upcall routine, designed to work as a key type and working through * /sbin/request-key to contact userspace when handling DNS queries. * * See Documentation/networking/dns_resolver.txt * * Copyright (c) 2007 Igor Mammedov * Author(s): Igor Mammedov (niallain@gmail.com) * Steve French (sfrench@us.ibm.com) * Wang Lei (wang840925@gmail.com) * David Howells (dhowells@redhat.com) * * The upcall wrapper used to make an arbitrary DNS query. * * This function requires the appropriate userspace tool dns.upcall to be * installed and something like the following lines should be added to the * /etc/request-key.conf file: * * create dns_resolver * * /sbin/dns.upcall %k * * For example to use this module to query AFSDB RR: * * create dns_resolver afsdb:* * /sbin/dns.afsdb %k * * This library is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published * by the Free Software Foundation; either version 2.1 of the License, or * (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See * the GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this library; if not, see . */ #include #include #include #include #include #include #include "internal.h" /** * dns_query - Query the DNS * @type: Query type (or NULL for straight host->IP lookup) * @name: Name to look up * @namelen: Length of name * @options: Request options (or NULL if no options) * @_result: Where to place the returned data. * @_expiry: Where to store the result expiry time (or NULL) * * The data will be returned in the pointer at *result, and the caller is * responsible for freeing it. * * The description should be of the form "[:]", and * the options need to be appropriate for the query type requested. If no * query_type is given, then the query is a straight hostname to IP address * lookup. * * The DNS resolution lookup is performed by upcalling to userspace by way of * requesting a key of type dns_resolver. * * Returns the size of the result on success, -ve error code otherwise. */ int dns_query(const char *type, const char *name, size_t namelen, const char *options, char **_result, time64_t *_expiry) { struct key *rkey; const struct user_key_payload *upayload; const struct cred *saved_cred; size_t typelen, desclen; char *desc, *cp; int ret, len; kenter("%s,%*.*s,%zu,%s", type, (int)namelen, (int)namelen, name, namelen, options); if (!name || namelen == 0 || !_result) return -EINVAL; /* construct the query key description as "[:]" */ typelen = 0; desclen = 0; if (type) { typelen = strlen(type); if (typelen < 1) return -EINVAL; desclen += typelen + 1; } if (!namelen) namelen = strnlen(name, 256); if (namelen < 3 || namelen > 255) return -EINVAL; desclen += namelen + 1; desc = kmalloc(desclen, GFP_KERNEL); if (!desc) return -ENOMEM; cp = desc; if (type) { memcpy(cp, type, typelen); cp += typelen; *cp++ = ':'; } memcpy(cp, name, namelen); cp += namelen; *cp = '\0'; if (!options) options = ""; kdebug("call request_key(,%s,%s)", desc, options); /* make the upcall, using special credentials to prevent the use of * add_key() to preinstall malicious redirections */ saved_cred = override_creds(dns_resolver_cache); rkey = request_key(&key_type_dns_resolver, desc, options); revert_creds(saved_cred); kfree(desc); if (IS_ERR(rkey)) { ret = PTR_ERR(rkey); goto out; } down_read(&rkey->sem); set_bit(KEY_FLAG_ROOT_CAN_INVAL, &rkey->flags); rkey->perm |= KEY_USR_VIEW; ret = key_validate(rkey); if (ret < 0) goto put; /* If the DNS server gave an error, return that to the caller */ ret = PTR_ERR(rkey->payload.data[dns_key_error]); if (ret) goto put; upayload = user_key_payload(rkey); len = upayload->datalen; ret = -ENOMEM; *_result = kmalloc(len + 1, GFP_KERNEL); if (!*_result) goto put; memcpy(*_result, upayload->data, len); (*_result)[len] = '\0'; if (_expiry) *_expiry = rkey->expiry; ret = len; put: up_read(&rkey->sem); key_put(rkey); out: kleave(" = %d", ret); return ret; } EXPORT_SYMBOL(dns_query); rvices Codepoint: Default (0) .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0) .... .... .... 0001 1100 1110 0100 1001 = Flow Label: 0x1ce49 Payload Length: 32 Next Header: TCP (6) (payload) Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2:: 0110 .... = Version: 6 .... 0000 0010 .... .... .... .... .... = Traffic Class: 0x02 (DSCP: CS0, ECN: ECT(0)) .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0) .... .... ..10 .... .... .... .... .... = Explicit Congestion Notification: ECN-Capable Transport codepoint '10' (2) .... .... .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000 Payload Length: 688 Next Header: TCP (6) This patch allows ip6_make_flowlabel() to be passed more than just a flow label and has it extract the part it really wants. This was simpler than modifying the callers. With this patch packets like the above become Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2:: 0110 .... = Version: 6 .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT) .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0) .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0) .... .... .... 1010 1111 1010 0101 1110 = Flow Label: 0xafa5e Payload Length: 32 Next Header: TCP (6) Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2:: 0110 .... = Version: 6 .... 0000 0010 .... .... .... .... .... = Traffic Class: 0x02 (DSCP: CS0, ECN: ECT(0)) .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0) .... .... ..10 .... .... .... .... .... = Explicit Congestion Notification: ECN-Capable Transport codepoint '10' (2) .... .... .... 1010 1111 1010 0101 1110 = Flow Label: 0xafa5e Payload Length: 688 Next Header: TCP (6) Signed-off-by: Dimitris Michailidis <dmichail@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>