1 /* SPDX-License-Identifier: BSD-3-Clause */
2 /*
3  * Copyright (c) 2013
4  * Guillaume Subiron
5  */
6 
7 #include "slirp.h"
8 #include "udp.h"
9 #include "dhcpv6.h"
10 
udp6_input(struct mbuf * m)11 void udp6_input(struct mbuf *m)
12 {
13     Slirp *slirp = m->slirp;
14     M_DUP_DEBUG(slirp, m, 0, 0);
15 
16     struct ip6 *ip, save_ip;
17     struct udphdr *uh;
18     int iphlen = sizeof(struct ip6);
19     int len;
20     struct socket *so;
21     struct sockaddr_in6 lhost;
22     int hop_limit;
23 
24     DEBUG_CALL("udp6_input");
25     DEBUG_ARG("m = %p", m);
26 
27     if (slirp->restricted) {
28         goto bad;
29     }
30 
31     ip = mtod(m, struct ip6 *);
32     m->m_len -= iphlen;
33     m->m_data += iphlen;
34     uh = mtod_check(m, sizeof(struct udphdr));
35     if (uh == NULL) {
36         goto bad;
37     }
38     m->m_len += iphlen;
39     m->m_data -= iphlen;
40 
41     if (ip6_cksum(m)) {
42         goto bad;
43     }
44 
45     len = ntohs((uint16_t)uh->uh_ulen);
46 
47     /*
48      * Make mbuf data length reflect UDP length.
49      * If not enough data to reflect UDP length, drop.
50      */
51     if (ntohs(ip->ip_pl) != len) {
52         if (len > ntohs(ip->ip_pl)) {
53             goto bad;
54         }
55         m_adj(m, len - ntohs(ip->ip_pl));
56         ip->ip_pl = htons(len);
57     }
58 
59     /*
60      * Save a copy of the IP header in case we want restore it
61      * for sending an ICMP error message in response.
62      */
63     save_ip = *ip;
64 
65     /* Locate pcb for datagram. */
66     lhost.sin6_family = AF_INET6;
67     lhost.sin6_addr = ip->ip_src;
68     lhost.sin6_port = uh->uh_sport;
69 
70     /* handle DHCPv6 */
71     if (ntohs(uh->uh_dport) == DHCPV6_SERVER_PORT &&
72         (in6_equal(&ip->ip_dst, &slirp->vhost_addr6) ||
73          in6_dhcp_multicast(&ip->ip_dst))) {
74         m->m_data += iphlen;
75         m->m_len -= iphlen;
76         dhcpv6_input(&lhost, m);
77         m->m_data -= iphlen;
78         m->m_len += iphlen;
79         goto bad;
80     }
81 
82     /* handle TFTP */
83     if (ntohs(uh->uh_dport) == TFTP_SERVER &&
84         !memcmp(ip->ip_dst.s6_addr, slirp->vhost_addr6.s6_addr, 16)) {
85         m->m_data += iphlen;
86         m->m_len -= iphlen;
87         tftp_input((struct sockaddr_storage *)&lhost, m);
88         m->m_data -= iphlen;
89         m->m_len += iphlen;
90         goto bad;
91     }
92 
93     so = solookup(&slirp->udp_last_so, &slirp->udb,
94                   (struct sockaddr_storage *)&lhost, NULL);
95 
96     if (so == NULL) {
97         /* If there's no socket for this packet, create one. */
98         so = socreate(slirp);
99         if (udp_attach(so, AF_INET6) == -1) {
100             DEBUG_MISC(" udp6_attach errno = %d-%s", errno, strerror(errno));
101             sofree(so);
102             goto bad;
103         }
104 
105         /* Setup fields */
106         so->so_lfamily = AF_INET6;
107         so->so_laddr6 = ip->ip_src;
108         so->so_lport6 = uh->uh_sport;
109     }
110 
111     so->so_ffamily = AF_INET6;
112     so->so_faddr6 = ip->ip_dst; /* XXX */
113     so->so_fport6 = uh->uh_dport; /* XXX */
114 
115     iphlen += sizeof(struct udphdr);
116     m->m_len -= iphlen;
117     m->m_data += iphlen;
118 
119     /*
120      * Check for TTL
121      */
122     hop_limit = save_ip.ip_hl-1;
123     if (hop_limit <= 0) {
124         m->m_len += iphlen;
125         m->m_data -= iphlen;
126         *ip = save_ip;
127         DEBUG_MISC("udp ttl exceeded");
128         icmp6_send_error(m, ICMP6_TIMXCEED, ICMP6_TIMXCEED_INTRANS);
129         goto bad;
130     }
131     setsockopt(so->s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &hop_limit, sizeof(hop_limit));
132 
133     /*
134      * Now we sendto() the packet.
135      */
136     if (sosendto(so, m) == -1) {
137         m->m_len += iphlen;
138         m->m_data -= iphlen;
139         *ip = save_ip;
140         DEBUG_MISC("udp tx errno = %d-%s", errno, strerror(errno));
141         icmp6_send_error(m, ICMP6_UNREACH, ICMP6_UNREACH_NO_ROUTE);
142         goto bad;
143     }
144 
145     m_free(so->so_m); /* used for ICMP if error on sorecvfrom */
146 
147     /* restore the orig mbuf packet */
148     m->m_len += iphlen;
149     m->m_data -= iphlen;
150     *ip = save_ip;
151     so->so_m = m;
152 
153     return;
154 bad:
155     m_free(m);
156 }
157 
udp6_output(struct socket * so,struct mbuf * m,struct sockaddr_in6 * saddr,struct sockaddr_in6 * daddr)158 int udp6_output(struct socket *so, struct mbuf *m, struct sockaddr_in6 *saddr,
159                 struct sockaddr_in6 *daddr)
160 {
161     Slirp *slirp = m->slirp;
162     M_DUP_DEBUG(slirp, m, 0, sizeof(struct ip6) + sizeof(struct udphdr));
163 
164     struct ip6 *ip;
165     struct udphdr *uh;
166 
167     DEBUG_CALL("udp6_output");
168     DEBUG_ARG("so = %p", so);
169     DEBUG_ARG("m = %p", m);
170 
171     /* adjust for header */
172     m->m_data -= sizeof(struct udphdr);
173     m->m_len += sizeof(struct udphdr);
174     uh = mtod(m, struct udphdr *);
175     m->m_data -= sizeof(struct ip6);
176     m->m_len += sizeof(struct ip6);
177     ip = mtod(m, struct ip6 *);
178 
179     /* Build IP header */
180     ip->ip_pl = htons(m->m_len - sizeof(struct ip6));
181     ip->ip_nh = IPPROTO_UDP;
182     ip->ip_src = saddr->sin6_addr;
183     ip->ip_dst = daddr->sin6_addr;
184 
185     /* Build UDP header */
186     uh->uh_sport = saddr->sin6_port;
187     uh->uh_dport = daddr->sin6_port;
188     uh->uh_ulen = ip->ip_pl;
189     uh->uh_sum = 0;
190     uh->uh_sum = ip6_cksum(m);
191     if (uh->uh_sum == 0) {
192         uh->uh_sum = 0xffff;
193     }
194 
195     return ip6_output(so, m, 0);
196 }
197