resolved: add a DNS client stub resolver

Let's turn resolved into a something truly useful: a fully asynchronous
DNS stub resolver that subscribes to network changes.

(More to come: caching, LLMNR, mDNS/DNS-SD, DNSSEC, IDN, NSS module)

1 files changed, 381 insertions, 0 deletions

diff --git a/src/resolve/resolved-dns-domain.c b/src/resolve/resolved-dns-domain.c
new file mode 100644
index 0000000000..94ffc0fac4
--- /dev/null
+++ b/src/resolve/resolved-dns-domain.c
@@ -0,0 +1,381 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 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 "resolved-dns-domain.h"
+
+int dns_label_unescape(const char **name, char *dest, size_t sz) {
+        const char *n;
+        char *d;
+        int r = 0;
+
+        assert(name);
+        assert(*name);
+        assert(dest);
+
+        n = *name;
+        d = dest;
+
+        for (;;) {
+                if (*n == '.') {
+                        n++;
+                        break;
+                }
+
+                if (*n == 0)
+                        break;
+
+                if (sz <= 0)
+                        return -ENOSPC;
+
+                if (*n == '\\') {
+                        /* Escaped character */
+
+                        n++;
+
+                        if (*n == 0)
+                                /* Ending NUL */
+                                return -EINVAL;
+
+                        else if (*n == '\\' || *n == '.') {
+                                /* Escaped backslash or dot */
+                                *(d++) = *(n++);
+                                sz--;
+                                r++;
+
+                        } else if (n[0] >= '0' && n[0] <= '9') {
+                                unsigned k;
+
+                                /* Escaped literal ASCII character */
+
+                                if (!(n[1] >= '0' && n[1] <= '9') ||
+                                    !(n[2] >= '0' && n[2] <= '9'))
+                                        return -EINVAL;
+
+                                k = ((unsigned) (n[0] - '0') * 100) +
+                                        ((unsigned) (n[1] - '0') * 10) +
+                                        ((unsigned) (n[2] - '0'));
+
+                                /* Don't allow CC characters or anything that doesn't fit in 8bit */
+                                if (k < ' ' || k > 255 || k == 127)
+                                        return -EINVAL;
+
+                                *(d++) = (char) k;
+                                sz--;
+                                r++;
+
+                                n += 3;
+                        } else
+                                return -EINVAL;
+
+                } else if (*n >= ' ' && *n != 127) {
+
+                        /* Normal character */
+                        *(d++) = *(n++);
+                        sz--;
+                        r++;
+                } else
+                        return -EINVAL;
+        }
+
+        /* Empty label that is not at the end? */
+        if (r == 0 && *n)
+                return -EINVAL;
+
+        if (sz >= 1)
+                *d = 0;
+
+        *name = n;
+        return r;
+}
+
+int dns_label_escape(const char *p, size_t l, char **ret) {
+        _cleanup_free_ char *s = NULL;
+        char *q;
+        int r;
+
+        assert(p);
+        assert(ret);
+
+        s = malloc(l * 4 + 1);
+        if (!s)
+                return -ENOMEM;
+
+        q = s;
+        while (l > 0) {
+
+                if (*p == '.' || *p == '\\') {
+
+                        /* Dot or backslash */
+                        *(q++) = '\\';
+                        *(q++) = *p;
+
+                } else if (*p == '_' ||
+                           *p == '-' ||
+                           (*p >= '0' && *p <= '9') ||
+                           (*p >= 'a' && *p <= 'z') ||
+                           (*p >= 'A' && *p <= 'Z')) {
+
+                        /* Proper character */
+                        *(q++) = *p;
+                } else if (*p >= ' ' && *p != 127) {
+
+                        /* Everything else */
+                        *(q++) = '\\';
+                        *(q++) = '0' + (char) ((unsigned) *p / 100);
+                        *(q++) = '0' + (char) (((unsigned) *p / 10) % 10);
+                        *(q++) = '0' + (char) ((unsigned) *p % 10);
+
+                } else
+                        return -EINVAL;
+
+                p++;
+                l--;
+        }
+
+        *q = 0;
+        *ret = s;
+        r = q - s;
+        s = NULL;
+
+        return r;
+}
+
+int dns_name_normalize(const char *s, char **_ret) {
+        _cleanup_free_ char *ret = NULL;
+        size_t n = 0, allocated = 0;
+        const char *p = s;
+        bool first = true;
+        int r;
+
+        assert(s);
+        assert(_ret);
+
+        for (;;) {
+                _cleanup_free_ char *t = NULL;
+                char label[DNS_LABEL_MAX];
+
+                r = dns_label_unescape(&p, label, sizeof(label));
+                if (r < 0)
+                        return r;
+                if (r == 0) {
+                        if (*p != 0)
+                                return -EINVAL;
+                        break;
+                }
+
+                r = dns_label_escape(label, r, &t);
+                if (r < 0)
+                        return r;
+
+                if (!GREEDY_REALLOC(ret, allocated, n + !first + strlen(t) + 1))
+                        return -ENOMEM;
+
+                if (!first)
+                        ret[n++] = '.';
+                else
+                        first = false;
+
+                memcpy(ret + n, t, r);
+                n += r;
+        }
+
+        if (!GREEDY_REALLOC(ret, allocated, n + 1))
+                return -ENOMEM;
+
+        ret[n] = 0;
+        *_ret = ret;
+        ret = NULL;
+
+        return 0;
+}
+
+unsigned long dns_name_hash_func(const void *s, const uint8_t hash_key[HASH_KEY_SIZE]) {
+        const char *p = s;
+        unsigned long ul = 0;
+        int r;
+
+        assert(p);
+
+        while (*p) {
+                char label[DNS_LABEL_MAX+1];
+
+                r = dns_label_unescape(&p, label, sizeof(label));
+                if (r < 0)
+                        break;
+
+                label[r] = 0;
+                ascii_strlower(label);
+
+                ul = hash_key[0] * ul + ul + string_hash_func(label, hash_key);
+        }
+
+        return ul;
+}
+
+int dns_name_compare_func(const void *a, const void *b) {
+        const char *x = a, *y = b;
+        int r, q;
+
+        assert(a);
+        assert(b);
+
+        for (;;) {
+                char la[DNS_LABEL_MAX+1], lb[DNS_LABEL_MAX+1];
+
+                if (*x == 0 && *y == 0)
+                        return 0;
+
+                r = dns_label_unescape(&x, la, sizeof(la));
+                q = dns_label_unescape(&y, lb, sizeof(lb));
+                if (r < 0 || q < 0)
+                        return r - q;
+
+                la[r] = lb[q] = 0;
+                r = strcasecmp(la, lb);
+                if (r != 0)
+                        return r;
+        }
+}
+
+int dns_name_equal(const char *x, const char *y) {
+        int r, q;
+
+        assert(x);
+        assert(y);
+
+        for (;;) {
+                char la[DNS_LABEL_MAX+1], lb[DNS_LABEL_MAX+1];
+
+                if (*x == 0 && *y == 0)
+                        return true;
+
+                r = dns_label_unescape(&x, la, sizeof(la));
+                if (r < 0)
+                        return r;
+
+                q = dns_label_unescape(&y, lb, sizeof(lb));
+                if (q < 0)
+                        return q;
+
+                la[r] = lb[q] = 0;
+                if (strcasecmp(la, lb))
+                        return false;
+        }
+}
+
+int dns_name_endswith(const char *name, const char *suffix) {
+        const char *n, *s, *saved_n = NULL;
+        int r, q;
+
+        assert(name);
+        assert(suffix);
+
+        n = name;
+        s = suffix;
+
+        for (;;) {
+                char ln[DNS_LABEL_MAX+1], ls[DNS_LABEL_MAX+1];
+
+                r = dns_label_unescape(&n, ln, sizeof(ln));
+                if (r < 0)
+                        return r;
+
+                if (!saved_n)
+                        saved_n = n;
+
+                q = dns_label_unescape(&s, ls, sizeof(ls));
+                if (r < 0)
+                        return r;
+
+                if (r == 0 && q == 0)
+                        return true;
+                if (r == 0 && saved_n == n)
+                        return false;
+
+                ln[r] = ls[q] = 0;
+
+                if (r != q || strcasecmp(ln, ls)) {
+
+                        /* Not the same, let's jump back, and try with the next label again */
+                        s = suffix;
+                        n = saved_n;
+                        saved_n = NULL;
+                }
+        }
+}
+
+int dns_name_reverse(int family, const union in_addr_union *a, char **ret) {
+        const uint8_t *p;
+        int r;
+
+        assert(a);
+        assert(ret);
+
+        p = (const uint8_t*) a;
+
+        if (family == AF_INET)
+                r = asprintf(ret, "%u.%u.%u.%u.in-addr.arpa", p[3], p[2], p[1], p[0]);
+        else if (family == AF_INET6)
+                r = asprintf(ret, "%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.ip6.arpa",
+                             hexchar(p[15]), hexchar(p[14]), hexchar(p[13]), hexchar(p[12]),
+                             hexchar(p[11]), hexchar(p[10]), hexchar(p[ 9]), hexchar(p[ 8]),
+                             hexchar(p[ 7]), hexchar(p[ 6]), hexchar(p[ 5]), hexchar(p[ 4]),
+                             hexchar(p[ 3]), hexchar(p[ 2]), hexchar(p[ 1]), hexchar(p[ 0]));
+        else
+                return -EAFNOSUPPORT;
+        if (r < 0)
+                return -ENOMEM;
+
+        return 0;
+}
+
+int dns_name_root(const char *name) {
+        char label[DNS_LABEL_MAX+1];
+        int r;
+
+        assert(name);
+
+        r = dns_label_unescape(&name, label, sizeof(label));
+        if (r < 0)
+                return r;
+
+        return r == 0 && *name == 0;
+}
+
+int dns_name_single_label(const char *name) {
+        char label[DNS_LABEL_MAX+1];
+        int r;
+
+        assert(name);
+
+        r = dns_label_unescape(&name, label, sizeof(label));
+        if (r < 0)
+                return r;
+
+        if (r == 0)
+                return 0;
+
+        r = dns_label_unescape(&name, label, sizeof(label));
+        if (r < 0)
+                return r;
+
+        return r == 0 && *name == 0;
+}