Adding upstream version 247.3.upstream/247.3upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1414 insertions, 0 deletions

diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
new file mode 100644
index 0000000..ec42b29
--- /dev/null
+++ b/src/shared/dns-domain.c
@@ -0,0 +1,1414 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <endian.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <sys/socket.h>
+
+#include "alloc-util.h"
+#include "dns-domain.h"
+#include "hashmap.h"
+#include "hexdecoct.h"
+#include "hostname-util.h"
+#include "idn-util.h"
+#include "in-addr-util.h"
+#include "macro.h"
+#include "parse-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "utf8.h"
+
+int dns_label_unescape(const char **name, char *dest, size_t sz, DNSLabelFlags flags) {
+        const char *n;
+        char *d, last_char = 0;
+        int r = 0;
+
+        assert(name);
+        assert(*name);
+
+        n = *name;
+        d = dest;
+
+        for (;;) {
+                if (IN_SET(*n, 0, '.')) {
+                        if (FLAGS_SET(flags, DNS_LABEL_LDH) && last_char == '-')
+                                /* Trailing dash */
+                                return -EINVAL;
+
+                        if (n[0] == '.' && (n[1] != 0 || !FLAGS_SET(flags, DNS_LABEL_LEAVE_TRAILING_DOT)))
+                                n++;
+
+                        break;
+                }
+
+                if (r >= DNS_LABEL_MAX)
+                        return -EINVAL;
+
+                if (sz <= 0)
+                        return -ENOBUFS;
+
+                if (*n == '\\') {
+                        /* Escaped character */
+                        if (FLAGS_SET(flags, DNS_LABEL_NO_ESCAPES))
+                                return -EINVAL;
+
+                        n++;
+
+                        if (*n == 0)
+                                /* Ending NUL */
+                                return -EINVAL;
+
+                        else if (IN_SET(*n, '\\', '.')) {
+                                /* Escaped backslash or dot */
+
+                                if (FLAGS_SET(flags, DNS_LABEL_LDH))
+                                        return -EINVAL;
+
+                                last_char = *n;
+                                if (d)
+                                        *(d++) = *n;
+                                sz--;
+                                r++;
+                                n++;
+
+                        } 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 anything that doesn't
+                                 * fit in 8bit. Note that we do allow
+                                 * control characters, as some servers
+                                 * (e.g. cloudflare) are happy to
+                                 * generate labels with them
+                                 * inside. */
+                                if (k > 255)
+                                        return -EINVAL;
+
+                                if (FLAGS_SET(flags, DNS_LABEL_LDH) &&
+                                    !valid_ldh_char((char) k))
+                                        return -EINVAL;
+
+                                last_char = (char) k;
+                                if (d)
+                                        *(d++) = (char) k;
+                                sz--;
+                                r++;
+
+                                n += 3;
+                        } else
+                                return -EINVAL;
+
+                } else if ((uint8_t) *n >= (uint8_t) ' ' && *n != 127) {
+
+                        /* Normal character */
+
+                        if (FLAGS_SET(flags, DNS_LABEL_LDH)) {
+                                if (!valid_ldh_char(*n))
+                                        return -EINVAL;
+                                if (r == 0 && *n == '-')
+                                        /* Leading dash */
+                                        return -EINVAL;
+                        }
+
+                        last_char = *n;
+                        if (d)
+                                *(d++) = *n;
+                        sz--;
+                        r++;
+                        n++;
+                } else
+                        return -EINVAL;
+        }
+
+        /* Empty label that is not at the end? */
+        if (r == 0 && *n)
+                return -EINVAL;
+
+        /* More than one trailing dot? */
+        if (n[0] == '.' && !FLAGS_SET(flags, DNS_LABEL_LEAVE_TRAILING_DOT))
+                return -EINVAL;
+
+        if (sz >= 1 && d)
+                *d = 0;
+
+        *name = n;
+        return r;
+}
+
+/* @label_terminal: terminal character of a label, updated to point to the terminal character of
+ *                  the previous label (always skipping one dot) or to NULL if there are no more
+ *                  labels. */
+int dns_label_unescape_suffix(const char *name, const char **label_terminal, char *dest, size_t sz) {
+        const char *terminal;
+        int r;
+
+        assert(name);
+        assert(label_terminal);
+        assert(dest);
+
+        /* no more labels */
+        if (!*label_terminal) {
+                if (sz >= 1)
+                        *dest = 0;
+
+                return 0;
+        }
+
+        terminal = *label_terminal;
+        assert(IN_SET(*terminal, 0, '.'));
+
+        /* Skip current terminal character (and accept domain names ending it ".") */
+        if (*terminal == 0)
+                terminal--;
+        if (terminal >= name && *terminal == '.')
+                terminal--;
+
+        /* Point name to the last label, and terminal to the preceding terminal symbol (or make it a NULL pointer) */
+        for (;;) {
+                if (terminal < name) {
+                        /* Reached the first label, so indicate that there are no more */
+                        terminal = NULL;
+                        break;
+                }
+
+                /* Find the start of the last label */
+                if (*terminal == '.') {
+                        const char *y;
+                        unsigned slashes = 0;
+
+                        for (y = terminal - 1; y >= name && *y == '\\'; y--)
+                                slashes++;
+
+                        if (slashes % 2 == 0) {
+                                /* The '.' was not escaped */
+                                name = terminal + 1;
+                                break;
+                        } else {
+                                terminal = y;
+                                continue;
+                        }
+                }
+
+                terminal--;
+        }
+
+        r = dns_label_unescape(&name, dest, sz, 0);
+        if (r < 0)
+                return r;
+
+        *label_terminal = terminal;
+
+        return r;
+}
+
+int dns_label_escape(const char *p, size_t l, char *dest, size_t sz) {
+        char *q;
+
+        /* DNS labels must be between 1 and 63 characters long. A
+         * zero-length label does not exist. See RFC 2182, Section
+         * 11. */
+
+        if (l <= 0 || l > DNS_LABEL_MAX)
+                return -EINVAL;
+        if (sz < 1)
+                return -ENOBUFS;
+
+        assert(p);
+        assert(dest);
+
+        q = dest;
+        while (l > 0) {
+
+                if (IN_SET(*p, '.', '\\')) {
+
+                        /* Dot or backslash */
+
+                        if (sz < 3)
+                                return -ENOBUFS;
+
+                        *(q++) = '\\';
+                        *(q++) = *p;
+
+                        sz -= 2;
+
+                } else if (IN_SET(*p, '_', '-') ||
+                           (*p >= '0' && *p <= '9') ||
+                           (*p >= 'a' && *p <= 'z') ||
+                           (*p >= 'A' && *p <= 'Z')) {
+
+                        /* Proper character */
+
+                        if (sz < 2)
+                                return -ENOBUFS;
+
+                        *(q++) = *p;
+                        sz -= 1;
+
+                } else {
+
+                        /* Everything else */
+
+                        if (sz < 5)
+                                return -ENOBUFS;
+
+                        *(q++) = '\\';
+                        *(q++) = '0' + (char) ((uint8_t) *p / 100);
+                        *(q++) = '0' + (char) (((uint8_t) *p / 10) % 10);
+                        *(q++) = '0' + (char) ((uint8_t) *p % 10);
+
+                        sz -= 4;
+                }
+
+                p++;
+                l--;
+        }
+
+        *q = 0;
+        return (int) (q - dest);
+}
+
+int dns_label_escape_new(const char *p, size_t l, char **ret) {
+        _cleanup_free_ char *s = NULL;
+        int r;
+
+        assert(p);
+        assert(ret);
+
+        if (l <= 0 || l > DNS_LABEL_MAX)
+                return -EINVAL;
+
+        s = new(char, DNS_LABEL_ESCAPED_MAX);
+        if (!s)
+                return -ENOMEM;
+
+        r = dns_label_escape(p, l, s, DNS_LABEL_ESCAPED_MAX);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(s);
+
+        return r;
+}
+
+#if HAVE_LIBIDN
+int dns_label_apply_idna(const char *encoded, size_t encoded_size, char *decoded, size_t decoded_max) {
+        _cleanup_free_ uint32_t *input = NULL;
+        size_t input_size, l;
+        const char *p;
+        bool contains_8bit = false;
+        char buffer[DNS_LABEL_MAX+1];
+        int r;
+
+        assert(encoded);
+        assert(decoded);
+
+        /* Converts an U-label into an A-label */
+
+        r = dlopen_idn();
+        if (r < 0)
+                return r;
+
+        if (encoded_size <= 0)
+                return -EINVAL;
+
+        for (p = encoded; p < encoded + encoded_size; p++)
+                if ((uint8_t) *p > 127)
+                        contains_8bit = true;
+
+        if (!contains_8bit) {
+                if (encoded_size > DNS_LABEL_MAX)
+                        return -EINVAL;
+
+                return 0;
+        }
+
+        input = sym_stringprep_utf8_to_ucs4(encoded, encoded_size, &input_size);
+        if (!input)
+                return -ENOMEM;
+
+        if (sym_idna_to_ascii_4i(input, input_size, buffer, 0) != 0)
+                return -EINVAL;
+
+        l = strlen(buffer);
+
+        /* Verify that the result is not longer than one DNS label. */
+        if (l <= 0 || l > DNS_LABEL_MAX)
+                return -EINVAL;
+        if (l > decoded_max)
+                return -ENOBUFS;
+
+        memcpy(decoded, buffer, l);
+
+        /* If there's room, append a trailing NUL byte, but only then */
+        if (decoded_max > l)
+                decoded[l] = 0;
+
+        return (int) l;
+}
+
+int dns_label_undo_idna(const char *encoded, size_t encoded_size, char *decoded, size_t decoded_max) {
+        size_t input_size, output_size;
+        _cleanup_free_ uint32_t *input = NULL;
+        _cleanup_free_ char *result = NULL;
+        uint32_t *output = NULL;
+        size_t w;
+        int r;
+
+        /* To be invoked after unescaping. Converts an A-label into an U-label. */
+
+        assert(encoded);
+        assert(decoded);
+
+        r = dlopen_idn();
+        if (r < 0)
+                return r;
+
+        if (encoded_size <= 0 || encoded_size > DNS_LABEL_MAX)
+                return -EINVAL;
+
+        if (!memory_startswith(encoded, encoded_size, IDNA_ACE_PREFIX))
+                return 0;
+
+        input = sym_stringprep_utf8_to_ucs4(encoded, encoded_size, &input_size);
+        if (!input)
+                return -ENOMEM;
+
+        output_size = input_size;
+        output = newa(uint32_t, output_size);
+
+        sym_idna_to_unicode_44i(input, input_size, output, &output_size, 0);
+
+        result = sym_stringprep_ucs4_to_utf8(output, output_size, NULL, &w);
+        if (!result)
+                return -ENOMEM;
+        if (w <= 0)
+                return -EINVAL;
+        if (w > decoded_max)
+                return -ENOBUFS;
+
+        memcpy(decoded, result, w);
+
+        /* Append trailing NUL byte if there's space, but only then. */
+        if (decoded_max > w)
+                decoded[w] = 0;
+
+        return w;
+}
+#endif
+
+int dns_name_concat(const char *a, const char *b, DNSLabelFlags flags, char **_ret) {
+        _cleanup_free_ char *ret = NULL;
+        size_t n = 0, allocated = 0;
+        const char *p;
+        bool first = true;
+        int r;
+
+        if (a)
+                p = a;
+        else if (b)
+                p = TAKE_PTR(b);
+        else
+                goto finish;
+
+        for (;;) {
+                char label[DNS_LABEL_MAX];
+
+                r = dns_label_unescape(&p, label, sizeof label, flags);
+                if (r < 0)
+                        return r;
+                if (r == 0) {
+                        if (*p != 0)
+                                return -EINVAL;
+
+                        if (b) {
+                                /* Now continue with the second string, if there is one */
+                                p = TAKE_PTR(b);
+                                continue;
+                        }
+
+                        break;
+                }
+
+                if (_ret) {
+                        if (!GREEDY_REALLOC(ret, allocated, n + !first + DNS_LABEL_ESCAPED_MAX))
+                                return -ENOMEM;
+
+                        r = dns_label_escape(label, r, ret + n + !first, DNS_LABEL_ESCAPED_MAX);
+                        if (r < 0)
+                                return r;
+
+                        if (!first)
+                                ret[n] = '.';
+                } else {
+                        char escaped[DNS_LABEL_ESCAPED_MAX];
+
+                        r = dns_label_escape(label, r, escaped, sizeof(escaped));
+                        if (r < 0)
+                                return r;
+                }
+
+                if (!first)
+                        n++;
+                else
+                        first = false;
+
+                n += r;
+        }
+
+finish:
+        if (n > DNS_HOSTNAME_MAX)
+                return -EINVAL;
+
+        if (_ret) {
+                if (n == 0) {
+                        /* Nothing appended? If so, generate at least a single dot, to indicate the DNS root domain */
+                        if (!GREEDY_REALLOC(ret, allocated, 2))
+                                return -ENOMEM;
+
+                        ret[n++] = '.';
+                } else {
+                        if (!GREEDY_REALLOC(ret, allocated, n + 1))
+                                return -ENOMEM;
+                }
+
+                ret[n] = 0;
+                *_ret = TAKE_PTR(ret);
+        }
+
+        return 0;
+}
+
+void dns_name_hash_func(const char *p, struct siphash *state) {
+        int r;
+
+        assert(p);
+
+        for (;;) {
+                char label[DNS_LABEL_MAX+1];
+
+                r = dns_label_unescape(&p, label, sizeof label, 0);
+                if (r < 0)
+                        break;
+                if (r == 0)
+                        break;
+
+                ascii_strlower_n(label, r);
+                siphash24_compress(label, r, state);
+                siphash24_compress_byte(0, state); /* make sure foobar and foo.bar result in different hashes */
+        }
+
+        /* enforce that all names are terminated by the empty label */
+        string_hash_func("", state);
+}
+
+int dns_name_compare_func(const char *a, const char *b) {
+        const char *x, *y;
+        int r, q;
+
+        assert(a);
+        assert(b);
+
+        x = a + strlen(a);
+        y = b + strlen(b);
+
+        for (;;) {
+                char la[DNS_LABEL_MAX], lb[DNS_LABEL_MAX];
+
+                if (x == NULL && y == NULL)
+                        return 0;
+
+                r = dns_label_unescape_suffix(a, &x, la, sizeof(la));
+                q = dns_label_unescape_suffix(b, &y, lb, sizeof(lb));
+                if (r < 0 || q < 0)
+                        return CMP(r, q);
+
+                r = ascii_strcasecmp_nn(la, r, lb, q);
+                if (r != 0)
+                        return r;
+        }
+}
+
+DEFINE_HASH_OPS(dns_name_hash_ops, char, dns_name_hash_func, dns_name_compare_func);
+
+int dns_name_equal(const char *x, const char *y) {
+        int r, q;
+
+        assert(x);
+        assert(y);
+
+        for (;;) {
+                char la[DNS_LABEL_MAX], lb[DNS_LABEL_MAX];
+
+                r = dns_label_unescape(&x, la, sizeof la, 0);
+                if (r < 0)
+                        return r;
+
+                q = dns_label_unescape(&y, lb, sizeof lb, 0);
+                if (q < 0)
+                        return q;
+
+                if (r != q)
+                        return false;
+                if (r == 0)
+                        return true;
+
+                if (ascii_strcasecmp_n(la, lb, r) != 0)
+                        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], ls[DNS_LABEL_MAX];
+
+                r = dns_label_unescape(&n, ln, sizeof ln, 0);
+                if (r < 0)
+                        return r;
+
+                if (!saved_n)
+                        saved_n = n;
+
+                q = dns_label_unescape(&s, ls, sizeof ls, 0);
+                if (q < 0)
+                        return q;
+
+                if (r == 0 && q == 0)
+                        return true;
+                if (r == 0 && saved_n == n)
+                        return false;
+
+                if (r != q || ascii_strcasecmp_n(ln, ls, r) != 0) {
+
+                        /* Not the same, let's jump back, and try with the next label again */
+                        s = suffix;
+                        n = TAKE_PTR(saved_n);
+                }
+        }
+}
+
+int dns_name_startswith(const char *name, const char *prefix) {
+        const char *n, *p;
+        int r, q;
+
+        assert(name);
+        assert(prefix);
+
+        n = name;
+        p = prefix;
+
+        for (;;) {
+                char ln[DNS_LABEL_MAX], lp[DNS_LABEL_MAX];
+
+                r = dns_label_unescape(&p, lp, sizeof lp, 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return true;
+
+                q = dns_label_unescape(&n, ln, sizeof ln, 0);
+                if (q < 0)
+                        return q;
+
+                if (r != q)
+                        return false;
+                if (ascii_strcasecmp_n(ln, lp, r) != 0)
+                        return false;
+        }
+}
+
+int dns_name_change_suffix(const char *name, const char *old_suffix, const char *new_suffix, char **ret) {
+        const char *n, *s, *saved_before = NULL, *saved_after = NULL, *prefix;
+        int r, q;
+
+        assert(name);
+        assert(old_suffix);
+        assert(new_suffix);
+        assert(ret);
+
+        n = name;
+        s = old_suffix;
+
+        for (;;) {
+                char ln[DNS_LABEL_MAX], ls[DNS_LABEL_MAX];
+
+                if (!saved_before)
+                        saved_before = n;
+
+                r = dns_label_unescape(&n, ln, sizeof ln, 0);
+                if (r < 0)
+                        return r;
+
+                if (!saved_after)
+                        saved_after = n;
+
+                q = dns_label_unescape(&s, ls, sizeof ls, 0);
+                if (q < 0)
+                        return q;
+
+                if (r == 0 && q == 0)
+                        break;
+                if (r == 0 && saved_after == n) {
+                        *ret = NULL; /* doesn't match */
+                        return 0;
+                }
+
+                if (r != q || ascii_strcasecmp_n(ln, ls, r) != 0) {
+
+                        /* Not the same, let's jump back, and try with the next label again */
+                        s = old_suffix;
+                        n = TAKE_PTR(saved_after);
+                        saved_before = NULL;
+                }
+        }
+
+        /* Found it! Now generate the new name */
+        prefix = strndupa(name, saved_before - name);
+
+        r = dns_name_concat(prefix, new_suffix, 0, ret);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+int dns_name_between(const char *a, const char *b, const char *c) {
+        /* Determine if b is strictly greater than a and strictly smaller than c.
+           We consider the order of names to be circular, so that if a is
+           strictly greater than c, we consider b to be between them if it is
+           either greater than a or smaller than c. This is how the canonical
+           DNS name order used in NSEC records work. */
+
+        if (dns_name_compare_func(a, c) < 0)
+                /*
+                   a and c are properly ordered:
+                   a<---b--->c
+                */
+                return dns_name_compare_func(a, b) < 0 &&
+                       dns_name_compare_func(b, c) < 0;
+        else
+                /*
+                   a and c are equal or 'reversed':
+                   <--b--c         a----->
+                   or:
+                   <-----c         a--b-->
+                */
+                return dns_name_compare_func(b, c) < 0 ||
+                       dns_name_compare_func(a, b) < 0;
+}
+
+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.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.%c.ip6.arpa",
+                             hexchar(p[15] & 0xF), hexchar(p[15] >> 4), hexchar(p[14] & 0xF), hexchar(p[14] >> 4),
+                             hexchar(p[13] & 0xF), hexchar(p[13] >> 4), hexchar(p[12] & 0xF), hexchar(p[12] >> 4),
+                             hexchar(p[11] & 0xF), hexchar(p[11] >> 4), hexchar(p[10] & 0xF), hexchar(p[10] >> 4),
+                             hexchar(p[ 9] & 0xF), hexchar(p[ 9] >> 4), hexchar(p[ 8] & 0xF), hexchar(p[ 8] >> 4),
+                             hexchar(p[ 7] & 0xF), hexchar(p[ 7] >> 4), hexchar(p[ 6] & 0xF), hexchar(p[ 6] >> 4),
+                             hexchar(p[ 5] & 0xF), hexchar(p[ 5] >> 4), hexchar(p[ 4] & 0xF), hexchar(p[ 4] >> 4),
+                             hexchar(p[ 3] & 0xF), hexchar(p[ 3] >> 4), hexchar(p[ 2] & 0xF), hexchar(p[ 2] >> 4),
+                             hexchar(p[ 1] & 0xF), hexchar(p[ 1] >> 4), hexchar(p[ 0] & 0xF), hexchar(p[ 0] >> 4));
+        else
+                return -EAFNOSUPPORT;
+        if (r < 0)
+                return -ENOMEM;
+
+        return 0;
+}
+
+int dns_name_address(const char *p, int *family, union in_addr_union *address) {
+        int r;
+
+        assert(p);
+        assert(family);
+        assert(address);
+
+        r = dns_name_endswith(p, "in-addr.arpa");
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                uint8_t a[4];
+                unsigned i;
+
+                for (i = 0; i < ELEMENTSOF(a); i++) {
+                        char label[DNS_LABEL_MAX+1];
+
+                        r = dns_label_unescape(&p, label, sizeof label, 0);
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                return -EINVAL;
+                        if (r > 3)
+                                return -EINVAL;
+
+                        r = safe_atou8(label, &a[i]);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = dns_name_equal(p, "in-addr.arpa");
+                if (r <= 0)
+                        return r;
+
+                *family = AF_INET;
+                address->in.s_addr = htobe32(((uint32_t) a[3] << 24) |
+                                             ((uint32_t) a[2] << 16) |
+                                             ((uint32_t) a[1] << 8) |
+                                              (uint32_t) a[0]);
+
+                return 1;
+        }
+
+        r = dns_name_endswith(p, "ip6.arpa");
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                struct in6_addr a;
+                unsigned i;
+
+                for (i = 0; i < ELEMENTSOF(a.s6_addr); i++) {
+                        char label[DNS_LABEL_MAX+1];
+                        int x, y;
+
+                        r = dns_label_unescape(&p, label, sizeof label, 0);
+                        if (r <= 0)
+                                return r;
+                        if (r != 1)
+                                return -EINVAL;
+                        x = unhexchar(label[0]);
+                        if (x < 0)
+                                return -EINVAL;
+
+                        r = dns_label_unescape(&p, label, sizeof label, 0);
+                        if (r <= 0)
+                                return r;
+                        if (r != 1)
+                                return -EINVAL;
+                        y = unhexchar(label[0]);
+                        if (y < 0)
+                                return -EINVAL;
+
+                        a.s6_addr[ELEMENTSOF(a.s6_addr) - i - 1] = (uint8_t) y << 4 | (uint8_t) x;
+                }
+
+                r = dns_name_equal(p, "ip6.arpa");
+                if (r <= 0)
+                        return r;
+
+                *family = AF_INET6;
+                address->in6 = a;
+                return 1;
+        }
+
+        return 0;
+}
+
+bool dns_name_is_root(const char *name) {
+
+        assert(name);
+
+        /* There are exactly two ways to encode the root domain name:
+         * as empty string, or with a single dot. */
+
+        return STR_IN_SET(name, "", ".");
+}
+
+bool dns_name_is_single_label(const char *name) {
+        int r;
+
+        assert(name);
+
+        r = dns_name_parent(&name);
+        if (r <= 0)
+                return false;
+
+        return dns_name_is_root(name);
+}
+
+/* Encode a domain name according to RFC 1035 Section 3.1, without compression */
+int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len, bool canonical) {
+        uint8_t *label_length, *out;
+        int r;
+
+        assert(domain);
+        assert(buffer);
+
+        out = buffer;
+
+        do {
+                /* Reserve a byte for label length */
+                if (len <= 0)
+                        return -ENOBUFS;
+                len--;
+                label_length = out;
+                out++;
+
+                /* Convert and copy a single label. Note that
+                 * dns_label_unescape() returns 0 when it hits the end
+                 * of the domain name, which we rely on here to encode
+                 * the trailing NUL byte. */
+                r = dns_label_unescape(&domain, (char *) out, len, 0);
+                if (r < 0)
+                        return r;
+
+                /* Optionally, output the name in DNSSEC canonical
+                 * format, as described in RFC 4034, section 6.2. Or
+                 * in other words: in lower-case. */
+                if (canonical)
+                        ascii_strlower_n((char*) out, (size_t) r);
+
+                /* Fill label length, move forward */
+                *label_length = r;
+                out += r;
+                len -= r;
+
+        } while (r != 0);
+
+        /* Verify the maximum size of the encoded name. The trailing
+         * dot + NUL byte account are included this time, hence
+         * compare against DNS_HOSTNAME_MAX + 2 (which is 255) this
+         * time. */
+        if (out - buffer > DNS_HOSTNAME_MAX + 2)
+                return -EINVAL;
+
+        return out - buffer;
+}
+
+static bool srv_type_label_is_valid(const char *label, size_t n) {
+        size_t k;
+
+        assert(label);
+
+        if (n < 2) /* Label needs to be at least 2 chars long */
+                return false;
+
+        if (label[0] != '_') /* First label char needs to be underscore */
+                return false;
+
+        /* Second char must be a letter */
+        if (!(label[1] >= 'A' && label[1] <= 'Z') &&
+            !(label[1] >= 'a' && label[1] <= 'z'))
+                return false;
+
+        /* Third and further chars must be alphanumeric or a hyphen */
+        for (k = 2; k < n; k++) {
+                if (!(label[k] >= 'A' && label[k] <= 'Z') &&
+                    !(label[k] >= 'a' && label[k] <= 'z') &&
+                    !(label[k] >= '0' && label[k] <= '9') &&
+                    label[k] != '-')
+                        return false;
+        }
+
+        return true;
+}
+
+bool dns_srv_type_is_valid(const char *name) {
+        unsigned c = 0;
+        int r;
+
+        if (!name)
+                return false;
+
+        for (;;) {
+                char label[DNS_LABEL_MAX];
+
+                /* This more or less implements RFC 6335, Section 5.1 */
+
+                r = dns_label_unescape(&name, label, sizeof label, 0);
+                if (r < 0)
+                        return false;
+                if (r == 0)
+                        break;
+
+                if (c >= 2)
+                        return false;
+
+                if (!srv_type_label_is_valid(label, r))
+                        return false;
+
+                c++;
+        }
+
+        return c == 2; /* exactly two labels */
+}
+
+bool dnssd_srv_type_is_valid(const char *name) {
+        return dns_srv_type_is_valid(name) &&
+                ((dns_name_endswith(name, "_tcp") > 0) ||
+                 (dns_name_endswith(name, "_udp") > 0)); /* Specific to DNS-SD. RFC 6763, Section 7 */
+}
+
+bool dns_service_name_is_valid(const char *name) {
+        size_t l;
+
+        /* This more or less implements RFC 6763, Section 4.1.1 */
+
+        if (!name)
+                return false;
+
+        if (!utf8_is_valid(name))
+                return false;
+
+        if (string_has_cc(name, NULL))
+                return false;
+
+        l = strlen(name);
+        if (l <= 0)
+                return false;
+        if (l > 63)
+                return false;
+
+        return true;
+}
+
+int dns_service_join(const char *name, const char *type, const char *domain, char **ret) {
+        char escaped[DNS_LABEL_ESCAPED_MAX];
+        _cleanup_free_ char *n = NULL;
+        int r;
+
+        assert(type);
+        assert(domain);
+        assert(ret);
+
+        if (!dns_srv_type_is_valid(type))
+                return -EINVAL;
+
+        if (!name)
+                return dns_name_concat(type, domain, 0, ret);
+
+        if (!dns_service_name_is_valid(name))
+                return -EINVAL;
+
+        r = dns_label_escape(name, strlen(name), escaped, sizeof(escaped));
+        if (r < 0)
+                return r;
+
+        r = dns_name_concat(type, domain, 0, &n);
+        if (r < 0)
+                return r;
+
+        return dns_name_concat(escaped, n, 0, ret);
+}
+
+static bool dns_service_name_label_is_valid(const char *label, size_t n) {
+        char *s;
+
+        assert(label);
+
+        if (memchr(label, 0, n))
+                return false;
+
+        s = strndupa(label, n);
+        return dns_service_name_is_valid(s);
+}
+
+int dns_service_split(const char *joined, char **_name, char **_type, char **_domain) {
+        _cleanup_free_ char *name = NULL, *type = NULL, *domain = NULL;
+        const char *p = joined, *q = NULL, *d = NULL;
+        char a[DNS_LABEL_MAX], b[DNS_LABEL_MAX], c[DNS_LABEL_MAX];
+        int an, bn, cn, r;
+        unsigned x = 0;
+
+        assert(joined);
+
+        /* Get first label from the full name */
+        an = dns_label_unescape(&p, a, sizeof(a), 0);
+        if (an < 0)
+                return an;
+
+        if (an > 0) {
+                x++;
+
+                /* If there was a first label, try to get the second one */
+                bn = dns_label_unescape(&p, b, sizeof(b), 0);
+                if (bn < 0)
+                        return bn;
+
+                if (bn > 0) {
+                        x++;
+
+                        /* If there was a second label, try to get the third one */
+                        q = p;
+                        cn = dns_label_unescape(&p, c, sizeof(c), 0);
+                        if (cn < 0)
+                                return cn;
+
+                        if (cn > 0)
+                                x++;
+                } else
+                        cn = 0;
+        } else
+                an = 0;
+
+        if (x >= 2 && srv_type_label_is_valid(b, bn)) {
+
+                if (x >= 3 && srv_type_label_is_valid(c, cn)) {
+
+                        if (dns_service_name_label_is_valid(a, an)) {
+                                /* OK, got <name> . <type> . <type2> . <domain> */
+
+                                name = strndup(a, an);
+                                if (!name)
+                                        return -ENOMEM;
+
+                                type = strjoin(b, ".", c);
+                                if (!type)
+                                        return -ENOMEM;
+
+                                d = p;
+                                goto finish;
+                        }
+
+                } else if (srv_type_label_is_valid(a, an)) {
+
+                        /* OK, got <type> . <type2> . <domain> */
+
+                        name = NULL;
+
+                        type = strjoin(a, ".", b);
+                        if (!type)
+                                return -ENOMEM;
+
+                        d = q;
+                        goto finish;
+                }
+        }
+
+        name = NULL;
+        type = NULL;
+        d = joined;
+
+finish:
+        r = dns_name_normalize(d, 0, &domain);
+        if (r < 0)
+                return r;
+
+        if (_domain)
+                *_domain = TAKE_PTR(domain);
+
+        if (_type)
+                *_type = TAKE_PTR(type);
+
+        if (_name)
+                *_name = TAKE_PTR(name);
+
+        return 0;
+}
+
+static int dns_name_build_suffix_table(const char *name, const char *table[]) {
+        const char *p;
+        unsigned n = 0;
+        int r;
+
+        assert(name);
+        assert(table);
+
+        p = name;
+        for (;;) {
+                if (n > DNS_N_LABELS_MAX)
+                        return -EINVAL;
+
+                table[n] = p;
+                r = dns_name_parent(&p);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                n++;
+        }
+
+        return (int) n;
+}
+
+int dns_name_suffix(const char *name, unsigned n_labels, const char **ret) {
+        const char* labels[DNS_N_LABELS_MAX+1];
+        int n;
+
+        assert(name);
+        assert(ret);
+
+        n = dns_name_build_suffix_table(name, labels);
+        if (n < 0)
+                return n;
+
+        if ((unsigned) n < n_labels)
+                return -EINVAL;
+
+        *ret = labels[n - n_labels];
+        return (int) (n - n_labels);
+}
+
+int dns_name_skip(const char *a, unsigned n_labels, const char **ret) {
+        int r;
+
+        assert(a);
+        assert(ret);
+
+        for (; n_labels > 0; n_labels--) {
+                r = dns_name_parent(&a);
+                if (r < 0)
+                        return r;
+                if (r == 0) {
+                        *ret = "";
+                        return 0;
+                }
+        }
+
+        *ret = a;
+        return 1;
+}
+
+int dns_name_count_labels(const char *name) {
+        unsigned n = 0;
+        const char *p;
+        int r;
+
+        assert(name);
+
+        p = name;
+        for (;;) {
+                r = dns_name_parent(&p);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                if (n >= DNS_N_LABELS_MAX)
+                        return -EINVAL;
+
+                n++;
+        }
+
+        return (int) n;
+}
+
+int dns_name_equal_skip(const char *a, unsigned n_labels, const char *b) {
+        int r;
+
+        assert(a);
+        assert(b);
+
+        r = dns_name_skip(a, n_labels, &a);
+        if (r <= 0)
+                return r;
+
+        return dns_name_equal(a, b);
+}
+
+int dns_name_common_suffix(const char *a, const char *b, const char **ret) {
+        const char *a_labels[DNS_N_LABELS_MAX+1], *b_labels[DNS_N_LABELS_MAX+1];
+        int n = 0, m = 0, k = 0, r, q;
+
+        assert(a);
+        assert(b);
+        assert(ret);
+
+        /* Determines the common suffix of domain names a and b */
+
+        n = dns_name_build_suffix_table(a, a_labels);
+        if (n < 0)
+                return n;
+
+        m = dns_name_build_suffix_table(b, b_labels);
+        if (m < 0)
+                return m;
+
+        for (;;) {
+                char la[DNS_LABEL_MAX], lb[DNS_LABEL_MAX];
+                const char *x, *y;
+
+                if (k >= n || k >= m) {
+                        *ret = a_labels[n - k];
+                        return 0;
+                }
+
+                x = a_labels[n - 1 - k];
+                r = dns_label_unescape(&x, la, sizeof la, 0);
+                if (r < 0)
+                        return r;
+
+                y = b_labels[m - 1 - k];
+                q = dns_label_unescape(&y, lb, sizeof lb, 0);
+                if (q < 0)
+                        return q;
+
+                if (r != q || ascii_strcasecmp_n(la, lb, r) != 0) {
+                        *ret = a_labels[n - k];
+                        return 0;
+                }
+
+                k++;
+        }
+}
+
+int dns_name_apply_idna(const char *name, char **ret) {
+
+        /* Return negative on error, 0 if not implemented, positive on success. */
+
+#if HAVE_LIBIDN2 || HAVE_LIBIDN2
+        int r;
+
+        r = dlopen_idn();
+        if (r == -EOPNOTSUPP) {
+                *ret = NULL;
+                return 0;
+        }
+        if (r < 0)
+                return r;
+#endif
+
+#if HAVE_LIBIDN2
+        _cleanup_free_ char *t = NULL;
+
+        assert(name);
+        assert(ret);
+
+        /* First, try non-transitional mode (i.e. IDN2008 rules) */
+        r = sym_idn2_lookup_u8((uint8_t*) name, (uint8_t**) &t,
+                               IDN2_NFC_INPUT | IDN2_NONTRANSITIONAL);
+        if (r == IDN2_DISALLOWED) /* If that failed, because of disallowed characters, try transitional mode.
+                                   * (i.e. IDN2003 rules which supports some unicode chars IDN2008 doesn't allow). */
+                r = sym_idn2_lookup_u8((uint8_t*) name, (uint8_t**) &t,
+                                       IDN2_NFC_INPUT | IDN2_TRANSITIONAL);
+
+        log_debug("idn2_lookup_u8: %s → %s", name, t);
+        if (r == IDN2_OK) {
+                if (!startswith(name, "xn--")) {
+                        _cleanup_free_ char *s = NULL;
+
+                        r = sym_idn2_to_unicode_8z8z(t, &s, 0);
+                        if (r != IDN2_OK) {
+                                log_debug("idn2_to_unicode_8z8z(\"%s\") failed: %d/%s",
+                                          t, r, sym_idn2_strerror(r));
+                                return 0;
+                        }
+
+                        if (!streq_ptr(name, s)) {
+                                log_debug("idn2 roundtrip failed: \"%s\" → \"%s\" → \"%s\", ignoring.",
+                                          name, t, s);
+                                return 0;
+                        }
+                }
+
+                *ret = TAKE_PTR(t);
+
+                return 1; /* *ret has been written */
+        }
+
+        log_debug("idn2_lookup_u8(\"%s\") failed: %d/%s", name, r, sym_idn2_strerror(r));
+        if (r == IDN2_2HYPHEN)
+                /* The name has two hyphens — forbidden by IDNA2008 in some cases */
+                return 0;
+        if (IN_SET(r, IDN2_TOO_BIG_DOMAIN, IDN2_TOO_BIG_LABEL))
+                return -ENOSPC;
+        return -EINVAL;
+#elif HAVE_LIBIDN
+        _cleanup_free_ char *buf = NULL;
+        size_t n = 0, allocated = 0;
+        bool first = true;
+        int r, q;
+
+        assert(name);
+        assert(ret);
+
+        for (;;) {
+                char label[DNS_LABEL_MAX];
+
+                r = dns_label_unescape(&name, label, sizeof label, 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                q = dns_label_apply_idna(label, r, label, sizeof label);
+                if (q < 0)
+                        return q;
+                if (q > 0)
+                        r = q;
+
+                if (!GREEDY_REALLOC(buf, allocated, n + !first + DNS_LABEL_ESCAPED_MAX))
+                        return -ENOMEM;
+
+                r = dns_label_escape(label, r, buf + n + !first, DNS_LABEL_ESCAPED_MAX);
+                if (r < 0)
+                        return r;
+
+                if (first)
+                        first = false;
+                else
+                        buf[n++] = '.';
+
+                n += r;
+        }
+
+        if (n > DNS_HOSTNAME_MAX)
+                return -EINVAL;
+
+        if (!GREEDY_REALLOC(buf, allocated, n + 1))
+                return -ENOMEM;
+
+        buf[n] = 0;
+        *ret = TAKE_PTR(buf);
+
+        return 1;
+#else
+        *ret = NULL;
+        return 0;
+#endif
+}
+
+int dns_name_is_valid_or_address(const char *name) {
+        /* Returns > 0 if the specified name is either a valid IP address formatted as string or a valid DNS name */
+
+        if (isempty(name))
+                return 0;
+
+        if (in_addr_from_string_auto(name, NULL, NULL) >= 0)
+                return 1;
+
+        return dns_name_is_valid(name);
+}
+
+int dns_name_dot_suffixed(const char *name) {
+        const char *p = name;
+        int r;
+
+        for (;;) {
+                if (streq(p, "."))
+                        return true;
+
+                r = dns_label_unescape(&p, NULL, DNS_LABEL_MAX, DNS_LABEL_LEAVE_TRAILING_DOT);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return false;
+        }
+}