resolved: synthesize RRs for data from /etc/hosts

This way the difference between lookups via NSS and our native bus API should become minimal.

1 files changed, 448 insertions, 0 deletions

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 <http://www.gnu.org/licenses/>.
+***/
+
+#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;
+}