/*-*- 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 <netinet/tcp.h>

#include "missing.h"
#include "strv.h"
#include "socket-util.h"
#include "af-list.h"
#include "resolved-dns-domain.h"
#include "resolved-dns-scope.h"

#define SEND_TIMEOUT_USEC (2*USEC_PER_SEC)

int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int family) {
        DnsScope *s;

        assert(m);
        assert(ret);

        s = new0(DnsScope, 1);
        if (!s)
                return -ENOMEM;

        s->manager = m;
        s->link = l;
        s->protocol = protocol;
        s->family = family;

        LIST_PREPEND(scopes, m->dns_scopes, s);

        dns_scope_llmnr_membership(s, true);

        log_debug("New scope on link %s, protocol %s, family %s", l ? l->name : "*", dns_protocol_to_string(protocol), family == AF_UNSPEC ? "*" : af_to_name(family));

        *ret = s;
        return 0;
}

DnsScope* dns_scope_free(DnsScope *s) {
        DnsQueryTransaction *t;

        if (!s)
                return NULL;

        log_debug("Removing scope on link %s, protocol %s, family %s", s->link ? s->link->name : "*", dns_protocol_to_string(s->protocol), s->family == AF_UNSPEC ? "*" : af_to_name(s->family));

        dns_scope_llmnr_membership(s, false);

        while ((t = s->transactions)) {

                /* Abort the transaction, but make sure it is not
                 * freed while we still look at it */

                t->block_gc++;
                dns_query_transaction_complete(t, DNS_QUERY_ABORTED);
                t->block_gc--;

                dns_query_transaction_free(t);
        }

        dns_cache_flush(&s->cache);
        dns_zone_flush(&s->zone);

        LIST_REMOVE(scopes, s->manager->dns_scopes, s);
        strv_free(s->domains);
        free(s);

        return NULL;
}

DnsServer *dns_scope_get_server(DnsScope *s) {
        assert(s);

        if (s->protocol != DNS_PROTOCOL_DNS)
                return NULL;

        if (s->link)
                return link_get_dns_server(s->link);
        else
                return manager_get_dns_server(s->manager);
}

void dns_scope_next_dns_server(DnsScope *s) {
        assert(s);

        if (s->protocol != DNS_PROTOCOL_DNS)
                return;

        if (s->link)
                link_next_dns_server(s->link);
        else
                manager_next_dns_server(s->manager);
}

int dns_scope_send(DnsScope *s, DnsPacket *p) {
        union in_addr_union addr;
        int ifindex = 0, r;
        int family;
        uint16_t port;
        uint32_t mtu;
        int fd;

        assert(s);
        assert(p);
        assert(p->protocol == s->protocol);

        if (s->link) {
                mtu = s->link->mtu;
                ifindex = s->link->ifindex;
        } else
                mtu = manager_find_mtu(s->manager);

        if (s->protocol == DNS_PROTOCOL_DNS) {
                DnsServer *srv;

                if (DNS_PACKET_QDCOUNT(p) > 1)
                        return -ENOTSUP;

                srv = dns_scope_get_server(s);
                if (!srv)
                        return -ESRCH;

                family = srv->family;
                addr = srv->address;
                port = 53;

                if (p->size > DNS_PACKET_UNICAST_SIZE_MAX)
                        return -EMSGSIZE;

                if (p->size > mtu)
                        return -EMSGSIZE;

                if (family == AF_INET)
                        fd = manager_dns_ipv4_fd(s->manager);
                else if (family == AF_INET6)
                        fd = manager_dns_ipv6_fd(s->manager);
                else
                        return -EAFNOSUPPORT;
                if (fd < 0)
                        return fd;

        } else if (s->protocol == DNS_PROTOCOL_LLMNR) {

                if (DNS_PACKET_QDCOUNT(p) > 1)
                        return -ENOTSUP;

                family = s->family;
                port = 5355;

                if (family == AF_INET) {
                        addr.in = LLMNR_MULTICAST_IPV4_ADDRESS;
                        fd = manager_llmnr_ipv4_udp_fd(s->manager);
                } else if (family == AF_INET6) {
                        addr.in6 = LLMNR_MULTICAST_IPV6_ADDRESS;
                        fd = manager_llmnr_ipv6_udp_fd(s->manager);
                } else
                        return -EAFNOSUPPORT;
                if (fd < 0)
                        return fd;
        } else
                return -EAFNOSUPPORT;

        r = manager_send(s->manager, fd, ifindex, family, &addr, port, p);
        if (r < 0)
                return r;

        return 1;
}

int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *address, uint16_t port) {
        _cleanup_close_ int fd = -1;
        union sockaddr_union sa = {};
        socklen_t salen;
        static const int one = 1;
        int ret, r;

        assert(s);
        assert((family == AF_UNSPEC) == !address);

        if (family == AF_UNSPEC) {
                DnsServer *srv;

                srv = dns_scope_get_server(s);
                if (!srv)
                        return -ESRCH;

                sa.sa.sa_family = srv->family;
                if (srv->family == AF_INET) {
                        sa.in.sin_port = htobe16(port);
                        sa.in.sin_addr = srv->address.in;
                        salen = sizeof(sa.in);
                } else if (srv->family == AF_INET6) {
                        sa.in6.sin6_port = htobe16(port);
                        sa.in6.sin6_addr = srv->address.in6;
                        sa.in6.sin6_scope_id = s->link ? s->link->ifindex : 0;
                        salen = sizeof(sa.in6);
                } else
                        return -EAFNOSUPPORT;
        } else {
                sa.sa.sa_family = family;

                if (family == AF_INET) {
                        sa.in.sin_port = htobe16(port);
                        sa.in.sin_addr = address->in;
                        salen = sizeof(sa.in);
                } else if (family == AF_INET6) {
                        sa.in6.sin6_port = htobe16(port);
                        sa.in6.sin6_addr = address->in6;
                        sa.in6.sin6_scope_id = s->link ? s->link->ifindex : 0;
                        salen = sizeof(sa.in6);
                } else
                        return -EAFNOSUPPORT;
        }

        fd = socket(sa.sa.sa_family, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
        if (fd < 0)
                return -errno;

        r = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one));
        if (r < 0)
                return -errno;

        if (s->link) {
                uint32_t ifindex = htobe32(s->link->ifindex);

                if (sa.sa.sa_family == AF_INET) {
                        r = setsockopt(fd, IPPROTO_IP, IP_UNICAST_IF, &ifindex, sizeof(ifindex));
                        if (r < 0)
                                return -errno;
                } else if (sa.sa.sa_family == AF_INET6) {
                        r = setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_IF, &ifindex, sizeof(ifindex));
                        if (r < 0)
                                return -errno;
                }
        }

        if (s->protocol == DNS_PROTOCOL_LLMNR) {
                /* RFC 4795, section 2.5 requires the TTL to be set to 1 */

                if (sa.sa.sa_family == AF_INET) {
                        r = setsockopt(fd, IPPROTO_IP, IP_TTL, &one, sizeof(one));
                        if (r < 0)
                                return -errno;
                } else if (sa.sa.sa_family == AF_INET6) {
                        r = setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &one, sizeof(one));
                        if (r < 0)
                                return -errno;
                }
        }

        r = connect(fd, &sa.sa, salen);
        if (r < 0 && errno != EINPROGRESS)
                return -errno;

        ret = fd;
        fd = -1;

        return ret;
}

DnsScopeMatch dns_scope_good_domain(DnsScope *s, const char *domain) {
        char **i;

        assert(s);
        assert(domain);

        STRV_FOREACH(i, s->domains)
                if (dns_name_endswith(domain, *i) > 0)
                        return DNS_SCOPE_YES;

        if (dns_name_root(domain) != 0)
                return DNS_SCOPE_NO;

        if (is_localhost(domain))
                return DNS_SCOPE_NO;

        if (s->protocol == DNS_PROTOCOL_DNS) {
                if (dns_name_endswith(domain, "254.169.in-addr.arpa") == 0 &&
                    dns_name_endswith(domain, "0.8.e.f.ip6.arpa") == 0 &&
                    dns_name_single_label(domain) == 0)
                        return DNS_SCOPE_MAYBE;

                return DNS_SCOPE_NO;
        }

        if (s->protocol == DNS_PROTOCOL_MDNS) {
                if (dns_name_endswith(domain, "254.169.in-addr.arpa") > 0 ||
                    dns_name_endswith(domain, "0.8.e.f.ip6.arpa") > 0 ||
                    (dns_name_endswith(domain, "local") > 0 && dns_name_equal(domain, "local") == 0))
                        return DNS_SCOPE_MAYBE;

                return DNS_SCOPE_NO;
        }

        if (s->protocol == DNS_PROTOCOL_LLMNR) {
                if (dns_name_endswith(domain, "in-addr.arpa") > 0 ||
                    dns_name_endswith(domain, "ip6.arpa") > 0 ||
                    dns_name_single_label(domain) > 0)
                        return DNS_SCOPE_MAYBE;

                return DNS_SCOPE_NO;
        }

        assert_not_reached("Unknown scope protocol");
}

int dns_scope_good_key(DnsScope *s, DnsResourceKey *key) {
        assert(s);
        assert(key);

        if (s->protocol == DNS_PROTOCOL_DNS)
                return true;

        /* On mDNS and LLMNR, send A and AAAA queries only on the
         * respective scopes */

        if (s->family == AF_INET && key->class == DNS_CLASS_IN && key->type == DNS_TYPE_AAAA)
                return false;

        if (s->family == AF_INET6 && key->class == DNS_CLASS_IN && key->type == DNS_TYPE_A)
                return false;

        return true;
}

int dns_scope_llmnr_membership(DnsScope *s, bool b) {
        int fd;

        if (s->family == AF_INET) {
                struct ip_mreqn mreqn = {
                        .imr_multiaddr = LLMNR_MULTICAST_IPV4_ADDRESS,
                        .imr_ifindex = s->link->ifindex,
                };

                fd = manager_llmnr_ipv4_udp_fd(s->manager);
                if (fd < 0)
                        return fd;

                if (setsockopt(fd, IPPROTO_IP, b ? IP_ADD_MEMBERSHIP : IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn)) < 0)
                        return -errno;

        } else if (s->family == AF_INET6) {
                struct ipv6_mreq mreq = {
                        .ipv6mr_multiaddr = LLMNR_MULTICAST_IPV6_ADDRESS,
                        .ipv6mr_interface = s->link->ifindex,
                };

                fd = manager_llmnr_ipv6_udp_fd(s->manager);
                if (fd < 0)
                        return fd;

                if (setsockopt(fd, IPPROTO_IPV6, b ? IPV6_ADD_MEMBERSHIP : IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
                        return -errno;
        } else
                return -EAFNOSUPPORT;

        return 0;
}

int dns_scope_good_dns_server(DnsScope *s, int family, const union in_addr_union *address) {
        assert(s);
        assert(address);

        if (s->protocol != DNS_PROTOCOL_DNS)
                return 1;

        if (s->link)
                return !!link_find_dns_server(s->link,  family, address);
        else
                return !!manager_find_dns_server(s->manager, family, address);
}

static int dns_scope_make_reply_packet(DnsScope *s, uint16_t id, int rcode, DnsQuestion *q, DnsAnswer *a, DnsPacket **ret) {
        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
        unsigned i;
        int r;

        assert(s);

        if (q->n_keys <= 0 && a->n_rrs <= 0)
                return -EINVAL;

        r = dns_packet_new(&p, s->protocol, 0);
        if (r < 0)
                return r;

        DNS_PACKET_HEADER(p)->id = id;
        DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
                                                              1 /* qr */,
                                                              0 /* opcode */,
                                                              0 /* c */,
                                                              0 /* tc */,
                                                              0 /* t */,
                                                              0 /* (ra) */,
                                                              0 /* (ad) */,
                                                              0 /* (cd) */,
                                                              rcode));

        if (q) {
                for (i = 0; i < q->n_keys; i++) {
                        r = dns_packet_append_key(p, q->keys[i], NULL);
                        if (r < 0)
                                return r;
                }

                DNS_PACKET_HEADER(p)->qdcount = htobe16(q->n_keys);
        }

        if (a) {
                for (i = 0; i < a->n_rrs; i++) {
                        r = dns_packet_append_rr(p, a->rrs[i], NULL);
                        if (r < 0)
                                return r;
                }

                DNS_PACKET_HEADER(p)->ancount = htobe16(a->n_rrs);
        }

        *ret = p;
        p = NULL;

        return 0;
}

void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
        _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
        _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
        int r, fd;

        assert(s);
        assert(p);

        if (p->protocol != DNS_PROTOCOL_LLMNR)
                return;

        r = dns_packet_extract(p);
        if (r < 0) {
                log_debug("Failed to extract resources from incoming packet: %s", strerror(-r));
                return;
        }

        if (DNS_PACKET_C(p)) {
                /* FIXME: Somebody notified us about a likely conflict */
                return;
        }

        r = dns_zone_lookup(&s->zone, p->question, &answer);
        if (r < 0) {
                log_debug("Failed to lookup key: %s", strerror(-r));
                return;
        }
        if (r == 0)
                return;

        r = dns_scope_make_reply_packet(s, DNS_PACKET_ID(p), DNS_RCODE_SUCCESS, p->question, answer, &reply);
        if (r < 0) {
                log_debug("Failed to build reply packet: %s", strerror(-r));
                return;
        }

        if (stream)
                r = dns_stream_write_packet(stream, reply);
        else {
                if (p->family == AF_INET)
                        fd = manager_llmnr_ipv4_udp_fd(s->manager);
                else if (p->family == AF_INET6)
                        fd = manager_llmnr_ipv6_udp_fd(s->manager);
                else {
                        log_debug("Unknown protocol");
                        return;
                }
                if (fd < 0) {
                        log_debug("Failed to get reply socket: %s", strerror(-fd));
                        return;
                }

                r = manager_send(s->manager, fd, p->ifindex, p->family, &p->sender, p->sender_port, reply);
        }

        if (r < 0) {
                log_debug("Failed to send reply packet: %s", strerror(-r));
                return;
        }
}