From dd0bc0f1414cc1d0fa73a29470bd14944e4942d3 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Fri, 22 Jan 2016 12:24:20 +0100 Subject: resolved: synthesize RRs for data from /etc/hosts This way the difference between lookups via NSS and our native bus API should become minimal. --- src/resolve/resolved-etc-hosts.c | 448 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 448 insertions(+) create mode 100644 src/resolve/resolved-etc-hosts.c (limited to 'src/resolve/resolved-etc-hosts.c') diff --git a/src/resolve/resolved-etc-hosts.c b/src/resolve/resolved-etc-hosts.c new file mode 100644 index 0000000000..467754774f --- /dev/null +++ b/src/resolve/resolved-etc-hosts.c @@ -0,0 +1,448 @@ +/*** + This file is part of systemd. + + Copyright 2016 Lennart Poettering + + systemd 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. + + systemd 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 systemd; If not, see . +***/ + +#include "fd-util.h" +#include "fileio.h" +#include "hostname-util.h" +#include "resolved-etc-hosts.h" +#include "resolved-dns-synthesize.h" +#include "string-util.h" +#include "strv.h" +#include "time-util.h" + +/* Recheck /etc/hosts at most once every 2s */ +#define ETC_HOSTS_RECHECK_USEC (2*USEC_PER_SEC) + +typedef struct EtcHostsItem { + int family; + union in_addr_union address; + + char **names; +} EtcHostsItem; + +typedef struct EtcHostsItemByName { + char *name; + + EtcHostsItem **items; + size_t n_items, n_allocated; +} EtcHostsItemByName; + +void manager_etc_hosts_flush(Manager *m) { + EtcHostsItem *item; + EtcHostsItemByName *bn; + + while ((item = set_steal_first(m->etc_hosts_by_address))) { + strv_free(item->names); + free(item); + } + + while ((bn = hashmap_steal_first(m->etc_hosts_by_name))) { + free(bn->name); + free(bn->items); + free(bn); + } + + m->etc_hosts_by_address = set_free(m->etc_hosts_by_address); + m->etc_hosts_by_name = hashmap_free(m->etc_hosts_by_name); + + m->etc_hosts_mtime = USEC_INFINITY; +} + +static void etc_hosts_item_hash_func(const void *p, struct siphash *state) { + const EtcHostsItem *item = p; + + siphash24_compress(&item->family, sizeof(item->family), state); + + if (item->family == AF_INET) + siphash24_compress(&item->address.in, sizeof(item->address.in), state); + else if (item->family == AF_INET6) + siphash24_compress(&item->address.in6, sizeof(item->address.in6), state); +} + +static int etc_hosts_item_compare_func(const void *a, const void *b) { + const EtcHostsItem *x = a, *y = b; + + if (x->family != x->family) + return x->family - y->family; + + if (x->family == AF_INET) + return memcmp(&x->address.in.s_addr, &y->address.in.s_addr, sizeof(struct in_addr)); + + if (x->family == AF_INET6) + return memcmp(&x->address.in6.s6_addr, &y->address.in6.s6_addr, sizeof(struct in6_addr)); + + return trivial_compare_func(a, b); +} + +static const struct hash_ops etc_hosts_item_ops = { + .hash = etc_hosts_item_hash_func, + .compare = etc_hosts_item_compare_func, +}; + +static int add_item(Manager *m, int family, const union in_addr_union *address, char **names) { + + EtcHostsItem key = { + .family = family, + .address = *address, + }; + EtcHostsItem *item; + char **n; + int r; + + assert(m); + assert(address); + + r = in_addr_is_null(family, address); + if (r < 0) + return r; + if (r > 0) + /* This is an 0.0.0.0 or :: item, which we assume means that we shall map the specified hostname to + * nothing. */ + item = NULL; + else { + /* If this is a normal address, then, simply add entry mapping it to the specified names */ + + item = set_get(m->etc_hosts_by_address, &key); + if (item) { + r = strv_extend_strv(&item->names, names, true); + if (r < 0) + return log_oom(); + } else { + + r = set_ensure_allocated(&m->etc_hosts_by_address, &etc_hosts_item_ops); + if (r < 0) + return log_oom(); + + item = new0(EtcHostsItem, 1); + if (!item) + return log_oom(); + + item->family = family; + item->address = *address; + item->names = names; + + r = set_put(m->etc_hosts_by_address, item); + if (r < 0) { + free(item); + return log_oom(); + } + } + } + + STRV_FOREACH(n, names) { + EtcHostsItemByName *bn; + + bn = hashmap_get(m->etc_hosts_by_name, *n); + if (!bn) { + r = hashmap_ensure_allocated(&m->etc_hosts_by_name, &dns_name_hash_ops); + if (r < 0) + return log_oom(); + + bn = new0(EtcHostsItemByName, 1); + if (!bn) + return log_oom(); + + bn->name = strdup(*n); + if (!bn->name) { + free(bn); + return log_oom(); + } + + r = hashmap_put(m->etc_hosts_by_name, bn->name, bn); + if (r < 0) { + free(bn->name); + free(bn); + return log_oom(); + } + } + + if (item) { + if (!GREEDY_REALLOC(bn->items, bn->n_allocated, bn->n_items+1)) + return log_oom(); + + bn->items[bn->n_items++] = item; + } + } + + return 0; +} + +static int parse_line(Manager *m, unsigned nr, const char *line) { + _cleanup_free_ char *address = NULL; + _cleanup_strv_free_ char **names = NULL; + union in_addr_union in; + bool suppressed = false; + int family, r; + + assert(m); + assert(line); + + r = extract_first_word(&line, &address, NULL, EXTRACT_RELAX); + if (r < 0) + return log_error_errno(r, "Couldn't extract address, in line /etc/hosts:%u.", nr); + if (r == 0) { + log_error("Premature end of line, in line /etc/hosts:%u.", nr); + return -EINVAL; + } + + r = in_addr_from_string_auto(address, &family, &in); + if (r < 0) + return log_error_errno(r, "Address '%s' is invalid, in line /etc/hosts:%u.", address, nr); + + for (;;) { + _cleanup_free_ char *name = NULL; + + r = extract_first_word(&line, &name, NULL, EXTRACT_RELAX); + if (r < 0) + return log_error_errno(r, "Couldn't extract host name, in line /etc/hosts:%u.", nr); + if (r == 0) + break; + + r = dns_name_is_valid(name); + if (r <= 0) + return log_error_errno(r, "Hostname %s is not valid, ignoring, in line /etc/hosts:%u.", name, nr); + + if (is_localhost(name)) { + /* Suppress the "localhost" line that is often seen */ + suppressed = true; + continue; + } + + r = strv_push(&names, name); + if (r < 0) + return log_oom(); + + name = NULL; + } + + if (strv_isempty(names)) { + + if (suppressed) + return 0; + + log_error("Line is missing any host names, in line /etc/hosts:%u.", nr); + return -EINVAL; + } + + /* Takes possession of the names strv */ + r = add_item(m, family, &in, names); + if (r < 0) + return r; + + names = NULL; + return r; +} + +int manager_etc_hosts_read(Manager *m) { + _cleanup_fclose_ FILE *f = NULL; + char line[LINE_MAX]; + struct stat st; + usec_t ts; + unsigned nr = 0; + int r; + + assert_se(sd_event_now(m->event, clock_boottime_or_monotonic(), &ts) >= 0); + + /* See if we checked /etc/hosts recently already */ + if (m->etc_hosts_last != USEC_INFINITY && m->etc_hosts_last + ETC_HOSTS_RECHECK_USEC > ts) + return 0; + + m->etc_hosts_last = ts; + + if (m->etc_hosts_mtime != USEC_INFINITY) { + if (stat("/etc/hosts", &st) < 0) { + if (errno == ENOENT) { + r = 0; + goto clear; + } + + return log_error_errno(errno, "Failed to stat /etc/hosts: %m"); + } + + /* Did the mtime change? If not, there's no point in re-reading the file. */ + if (timespec_load(&st.st_mtim) == m->etc_hosts_mtime) + return 0; + } + + f = fopen("/etc/hosts", "re"); + if (!f) { + if (errno == ENOENT) { + r = 0; + goto clear; + } + + return log_error_errno(errno, "Failed to open /etc/hosts: %m"); + } + + /* Take the timestamp at the beginning of processing, so that any changes made later are read on the next + * invocation */ + r = fstat(fileno(f), &st); + if (r < 0) + return log_error_errno(errno, "Failed to fstat() /etc/hosts: %m"); + + manager_etc_hosts_flush(m); + + FOREACH_LINE(line, f, return log_error_errno(errno, "Failed to read /etc/hosts: %m")) { + char *l; + + nr ++; + + l = strstrip(line); + if (isempty(l)) + continue; + if (l[0] == '#') + continue; + + r = parse_line(m, nr, l); + if (r == -ENOMEM) /* On OOM we abandon the half-built-up structure. All other errors we ignore and proceed */ + goto clear; + } + + m->etc_hosts_mtime = timespec_load(&st.st_mtim); + m->etc_hosts_last = ts; + + return 1; + +clear: + manager_etc_hosts_flush(m); + return r; +} + +int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer) { + bool found_a = false, found_aaaa = false; + EtcHostsItemByName *bn; + EtcHostsItem k = {}; + DnsResourceKey *t; + const char *name; + unsigned i; + int r; + + assert(m); + assert(q); + assert(answer); + + r = manager_etc_hosts_read(m); + if (r < 0) + return r; + + name = dns_question_first_name(q); + if (!name) + return 0; + + r = dns_name_address(name, &k.family, &k.address); + if (r > 0) { + EtcHostsItem *item; + DnsResourceKey *found_ptr = NULL; + + item = set_get(m->etc_hosts_by_address, &k); + if (!item) + return 0; + + /* We have an address in /etc/hosts that matches the queried name. Let's return successful. Actual data + * we'll only return if the request was for PTR. */ + + DNS_QUESTION_FOREACH(t, q) { + if (!IN_SET(t->type, DNS_TYPE_PTR, DNS_TYPE_ANY)) + continue; + if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY)) + continue; + + r = dns_name_equal(DNS_RESOURCE_KEY_NAME(t), name); + if (r < 0) + return r; + if (r > 0) { + found_ptr = t; + break; + } + } + + if (found_ptr) { + char **n; + + r = dns_answer_reserve(answer, strv_length(item->names)); + if (r < 0) + return r; + + STRV_FOREACH(n, item->names) { + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; + + rr = dns_resource_record_new(found_ptr); + if (!rr) + return -ENOMEM; + + rr->ptr.name = strdup(*n); + if (!rr->ptr.name) + return -ENOMEM; + + r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED); + if (r < 0) + return r; + } + } + + return 1; + } + + bn = hashmap_get(m->etc_hosts_by_name, name); + if (!bn) + return 0; + + r = dns_answer_reserve(answer, bn->n_items); + if (r < 0) + return r; + + DNS_QUESTION_FOREACH(t, q) { + if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA, DNS_TYPE_ANY)) + continue; + if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY)) + continue; + + r = dns_name_equal(DNS_RESOURCE_KEY_NAME(t), name); + if (r < 0) + return r; + if (r == 0) + continue; + + if (IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_ANY)) + found_a = true; + if (IN_SET(t->type, DNS_TYPE_AAAA, DNS_TYPE_ANY)) + found_aaaa = true; + + if (found_a && found_aaaa) + break; + } + + for (i = 0; i < bn->n_items; i++) { + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; + + if ((found_a && bn->items[i]->family != AF_INET) && + (found_aaaa && bn->items[i]->family != AF_INET6)) + continue; + + r = dns_resource_record_new_address(&rr, bn->items[i]->family, &bn->items[i]->address, bn->name); + if (r < 0) + return r; + + r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED); + if (r < 0) + return r; + } + + return 1; +} -- cgit v1.2.3-54-g00ecf