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passt/dhcpv6.c
David Gibson 16f5586bb8 Make substructures for IPv4 and IPv6 specific context information 
The context structure contains a batch of fields specific to IPv4 and to
IPv6 connectivity.  Split those out into a sub-structure.

This allows the conf_ip4() and conf_ip6() functions, which take the
entire context but touch very little of it, to be given more specific
parameters, making it clearer what it affects without stepping through the
code.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2022-07-30 22:14:07 +02:00

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// SPDX-License-Identifier: AGPL-3.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* dhcpv6.c - Minimalistic DHCPv6 server for PASST
*
* Copyright (c) 2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*/
#include <arpa/inet.h>
#include <net/if_arp.h>
#include <net/if.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <netinet/if_ether.h>
#include <stdio.h>
#include <stddef.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <limits.h>
#include "packet.h"
#include "util.h"
#include "passt.h"
#include "tap.h"
/**
* struct opt_hdr - DHCPv6 option header
* @t: Option type
* @l: Option length, network order
*/
struct opt_hdr {
uint16_t t;
#if __BYTE_ORDER == __BIG_ENDIAN
# define OPT_CLIENTID 1
# define OPT_SERVERID 2
# define OPT_IA_NA 3
# define OPT_IA_TA 4
# define OPT_IAAADR 5
# define OPT_STATUS_CODE 13
# define STATUS_NOTONLINK 4
# define OPT_DNS_SERVERS 23
# define OPT_DNS_SEARCH 24
#else
# define OPT_CLIENTID __bswap_constant_16(1)
# define OPT_SERVERID __bswap_constant_16(2)
# define OPT_IA_NA __bswap_constant_16(3)
# define OPT_IA_TA __bswap_constant_16(4)
# define OPT_IAAADR __bswap_constant_16(5)
# define OPT_STATUS_CODE __bswap_constant_16(13)
# define STATUS_NOTONLINK __bswap_constant_16(4)
# define OPT_DNS_SERVERS __bswap_constant_16(23)
# define OPT_DNS_SEARCH __bswap_constant_16(24)
#endif
#define STR_NOTONLINK "Prefix not appropriate for link."
uint16_t l;
};
#if __BYTE_ORDER == __BIG_ENDIAN
# define OPT_SIZE_CONV(x) (x)
#else
# define OPT_SIZE_CONV(x) (__bswap_constant_16(x))
#endif
#define OPT_SIZE(x) OPT_SIZE_CONV(sizeof(struct opt_##x) - \
sizeof(struct opt_hdr))
#define OPT_VSIZE(x) (sizeof(struct opt_##x) - \
sizeof(struct opt_hdr))
/**
* struct opt_client_id - DHCPv6 Client Identifier option
* @hdr: Option header
* @duid: Client DUID, up to 128 bytes (cf. RFC 8415, 11.1.)
*/
struct opt_client_id {
struct opt_hdr hdr;
uint8_t duid[128];
};
/**
* struct opt_server_id - DHCPv6 Server Identifier option
* @hdr: Option header
* @duid_type: Type of server DUID, network order
* @duid_hw: IANA hardware type, network order
* @duid_time: Time reference, network order
* @duid_lladdr: Link-layer address (MAC address)
*/
struct opt_server_id {
struct opt_hdr hdr;
uint16_t duid_type;
#define DUID_TYPE_LLT 1
uint16_t duid_hw;
uint32_t duid_time;
uint8_t duid_lladdr[ETH_ALEN];
};
#if __BYTE_ORDER == __BIG_ENDIAN
#define SERVER_ID { \
{ OPT_SERVERID, OPT_SIZE(server_id) }, \
DUID_TYPE_LLT, ARPHRD_ETHER, 0, { 0 } \
}
#else
#define SERVER_ID { \
{ OPT_SERVERID, OPT_SIZE(server_id) }, \
__bswap_constant_16(DUID_TYPE_LLT), \
__bswap_constant_16(ARPHRD_ETHER), \
0, { 0 } \
}
#endif
/**
* struct opt_ia_na - Identity Association for Non-temporary Addresses Option
* @hdr: Option header
* @iaid: Unique identifier for IA_NA, network order
* @t1: Rebind interval for this server (always infinity)
* @t2: Rebind interval for any server (always infinity)
*/
struct opt_ia_na {
struct opt_hdr hdr;
uint32_t iaid;
uint32_t t1;
uint32_t t2;
};
/**
* struct opt_ia_ta - Identity Association for Temporary Addresses Option
* @hdr: Option header
* @iaid: Unique identifier for IA_TA, network order
*/
struct opt_ia_ta {
struct opt_hdr hdr;
uint32_t iaid;
};
/**
* struct opt_ia_addr - IA Address Option
* @hdr: Option header
* @addr: Leased IPv6 address
* @pref_lifetime: Preferred lifetime, network order (always infinity)
* @valid_lifetime: Valid lifetime, network order (always infinity)
*/
struct opt_ia_addr {
struct opt_hdr hdr;
struct in6_addr addr;
uint32_t pref_lifetime;
uint32_t valid_lifetime;
};
/**
* struct opt_status_code - Status Code Option (used for NotOnLink error only)
* @hdr: Option header
* @code: Numeric code for status, network order
* @status_msg: Text string suitable for display, not NULL-terminated
*/
struct opt_status_code {
struct opt_hdr hdr;
uint16_t code;
char status_msg[sizeof(STR_NOTONLINK) - 1];
};
/**
* struct opt_dns_servers - DNS Recursive Name Server option (RFC 3646)
* @hdr: Option header
* @addr: IPv6 DNS addresses
*/
struct opt_dns_servers {
struct opt_hdr hdr;
struct in6_addr addr[MAXNS];
};
/**
* struct opt_dns_servers - Domain Search List option (RFC 3646)
* @hdr: Option header
* @list: NULL-separated list of domain names
*/
struct opt_dns_search {
struct opt_hdr hdr;
char list[MAXDNSRCH * NS_MAXDNAME];
};
/**
* struct msg_hdr - DHCPv6 client/server message header
* @type: DHCP message type
* @xid: Transaction ID for message exchange
*/
struct msg_hdr {
uint32_t type:8;
#define TYPE_SOLICIT 1
#define TYPE_ADVERTISE 2
#define TYPE_REQUEST 3
#define TYPE_CONFIRM 4
#define TYPE_RENEW 5
#define TYPE_REBIND 6
#define TYPE_REPLY 7
#define TYPE_RELEASE 8
#define TYPE_DECLINE 9
#define TYPE_INFORMATION_REQUEST 11
uint32_t xid:24;
} __attribute__((__packed__));
#if __BYTE_ORDER == __BIG_ENDIAN
#define UH_RESP {{{ 547, 546, 0, 0, }}}
#else
#define UH_RESP {{{ __bswap_constant_16(547), __bswap_constant_16(546), 0, 0 }}}
#endif
/**
* struct resp_t - Normal advertise and reply message
* @uh: UDP header
* @hdr: DHCP message header
* @server_id: Server Identifier option
* @ia_na: Non-temporary Address option
* @ia_addr: Address for IA_NA
* @client_id: Client Identifier, variable length
* @dns_servers: DNS Recursive Name Server, here just for storage size
* @dns_search: Domain Search List, here just for storage size
*/
static struct resp_t {
struct udphdr uh;
struct msg_hdr hdr;
struct opt_server_id server_id;
struct opt_ia_na ia_na;
struct opt_ia_addr ia_addr;
struct opt_client_id client_id;
struct opt_dns_servers dns_servers;
struct opt_dns_search dns_search;
} __attribute__((__packed__)) resp = {
UH_RESP,
{ 0 },
SERVER_ID,
{ { OPT_IA_NA, OPT_SIZE_CONV(sizeof(struct opt_ia_na) +
sizeof(struct opt_ia_addr) -
sizeof(struct opt_hdr)) },
1, (uint32_t)~0U, (uint32_t)~0U
},
{ { OPT_IAAADR, OPT_SIZE(ia_addr) },
IN6ADDR_ANY_INIT, (uint32_t)~0U, (uint32_t)~0U
},
{ { OPT_CLIENTID, 0, },
{ 0 }
},
{ { OPT_DNS_SERVERS, 0, },
{ IN6ADDR_ANY_INIT }
},
{ { OPT_DNS_SEARCH, 0, },
{ 0 },
},
};
static const struct opt_status_code sc_not_on_link = {
{ OPT_STATUS_CODE, OPT_SIZE(status_code), },
STATUS_NOTONLINK, STR_NOTONLINK
};
/**
* struct resp_not_on_link_t - NotOnLink error (mandated by RFC 8415, 18.3.2.)
* @uh: UDP header
* @hdr: DHCP message header
* @server_id: Server Identifier option
* @var: Payload: IA_NA from client, status code, client ID
*/
static struct resp_not_on_link_t {
struct udphdr uh;
struct msg_hdr hdr;
struct opt_server_id server_id;
uint8_t var[sizeof(struct opt_ia_na) + sizeof(struct opt_status_code) +
sizeof(struct opt_client_id)];
} __attribute__((__packed__)) resp_not_on_link = {
UH_RESP,
{ TYPE_REPLY, 0 },
SERVER_ID,
{ 0, },
};
/**
* dhcpv6_opt() - Get option from DHCPv6 message
* @p: Packet pool, single packet with UDP header
* @offset: Offset to look at, 0: end of header, set to option start
* @type: Option type to look up, network order
*
* Return: pointer to option header, or NULL on malformed or missing option
*/
static struct opt_hdr *dhcpv6_opt(const struct pool *p, size_t *offset,
uint16_t type)
{
struct opt_hdr *o;
size_t left;
if (!*offset)
*offset = sizeof(struct udphdr) + sizeof(struct msg_hdr);
while ((o = packet_get_try(p, 0, *offset, sizeof(*o), &left))) {
unsigned int opt_len = ntohs(o->l) + sizeof(*o);
if (ntohs(o->l) > left)
return NULL;
if (o->t == type)
return o;
*offset += opt_len;
}
return NULL;
}
/**
* dhcpv6_ia_notonlink() - Check if any IA contains non-appropriate addresses
* @p: Packet pool, single packet starting from UDP header
* @la: Address we want to lease to the client
*
* Return: pointer to non-appropriate IA_NA or IA_TA, if any, NULL otherwise
*/
static struct opt_hdr *dhcpv6_ia_notonlink(const struct pool *p,
struct in6_addr *la)
{
char buf[INET6_ADDRSTRLEN];
struct in6_addr *req_addr;
struct opt_hdr *ia, *h;
size_t offset;
int ia_type;
ia_type = OPT_IA_NA;
ia_ta:
offset = 0;
while ((ia = dhcpv6_opt(p, &offset, ia_type))) {
if (ntohs(ia->l) < OPT_VSIZE(ia_na))
return NULL;
offset += sizeof(struct opt_ia_na);
while ((h = dhcpv6_opt(p, &offset, OPT_IAAADR))) {
struct opt_ia_addr *opt_addr = (struct opt_ia_addr *)h;
if (ntohs(h->l) != OPT_VSIZE(ia_addr))
return NULL;
req_addr = &opt_addr->addr;
if (!IN6_ARE_ADDR_EQUAL(la, req_addr)) {
info("DHCPv6: requested address %s not on link",
inet_ntop(AF_INET6, req_addr,
buf, sizeof(buf)));
return ia;
}
offset += sizeof(struct opt_ia_addr);
}
}
if (ia_type == OPT_IA_NA) {
ia_type = OPT_IA_TA;
goto ia_ta;
}
return NULL;
}
/**
* dhcpv6_dns_fill() - Fill in DNS Servers and Domain Search list options
* @c: Execution context
* @buf: Response message buffer where options will be appended
* @offset: Offset in message buffer for new options
*
* Return: updated length of response message buffer.
*/
static size_t dhcpv6_dns_fill(const struct ctx *c, char *buf, int offset)
{
struct opt_dns_servers *srv = NULL;
struct opt_dns_search *srch = NULL;
char *p = NULL;
int i;
if (c->no_dhcp_dns)
goto search;
for (i = 0; !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns[i]); i++) {
if (!i) {
srv = (struct opt_dns_servers *)(buf + offset);
offset += sizeof(struct opt_hdr);
srv->hdr.t = OPT_DNS_SERVERS;
srv->hdr.l = 0;
}
memcpy(&srv->addr[i], &c->ip6.dns[i], sizeof(srv->addr[i]));
srv->hdr.l += sizeof(srv->addr[i]);
offset += sizeof(srv->addr[i]);
}
if (srv)
srv->hdr.l = htons(srv->hdr.l);
search:
if (c->no_dhcp_dns_search)
return offset;
for (i = 0; *c->dns_search[i].n; i++) {
if (!i) {
srch = (struct opt_dns_search *)(buf + offset);
offset += sizeof(struct opt_hdr);
srch->hdr.t = OPT_DNS_SEARCH;
srch->hdr.l = 0;
p = srch->list;
*p = 0;
}
p = stpcpy(p + 1, c->dns_search[i].n);
*(p++) = 0;
srch->hdr.l += strlen(c->dns_search[i].n) + 2;
offset += strlen(c->dns_search[i].n) + 2;
}
if (srch) {
for (i = 0; i < srch->hdr.l; i++) {
if (srch->list[i] == '.' || !srch->list[i]) {
srch->list[i] = strcspn(srch->list + i + 1,
".");
}
}
srch->hdr.l = htons(srch->hdr.l);
}
return offset;
}
/**
* dhcpv6() - Check if this is a DHCPv6 message, reply as needed
* @c: Execution context
* @p: Packet pool, single packet starting from UDP header
* @saddr: Source IPv6 address of original message
* @daddr: Destination IPv6 address of original message
*
* Return: 0 if it's not a DHCPv6 message, 1 if handled, -1 on failure
*/
int dhcpv6(struct ctx *c, const struct pool *p,
const struct in6_addr *saddr, const struct in6_addr *daddr)
{
struct opt_hdr *ia, *bad_ia, *client_id, *server_id;
struct in6_addr *src;
struct msg_hdr *mh;
struct udphdr *uh;
size_t mlen, n;
uh = packet_get(p, 0, 0, sizeof(*uh), &mlen);
if (!uh)
return -1;
if (uh->dest != htons(547))
return 0;
if (c->no_dhcpv6)
return 1;
if (!IN6_IS_ADDR_MULTICAST(daddr))
return -1;
if (mlen + sizeof(*uh) != ntohs(uh->len) || mlen < sizeof(*mh))
return -1;
c->ip6.addr_ll_seen = *saddr;
if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
src = &c->ip6.gw;
else
src = &c->ip6.addr_ll;
mh = packet_get(p, 0, sizeof(*uh), sizeof(*mh), NULL);
if (!mh)
return -1;
client_id = dhcpv6_opt(p, &(size_t){ 0 }, OPT_CLIENTID);
if (!client_id || ntohs(client_id->l) > OPT_VSIZE(client_id))
return -1;
server_id = dhcpv6_opt(p, &(size_t){ 0 }, OPT_SERVERID);
if (server_id && ntohs(server_id->l) != OPT_VSIZE(server_id))
return -1;
ia = dhcpv6_opt(p, &(size_t){ 0 }, OPT_IA_NA);
if (ia && ntohs(ia->l) < MIN(OPT_VSIZE(ia_na), OPT_VSIZE(ia_ta)))
return -1;
resp.hdr.type = TYPE_REPLY;
switch (mh->type) {
case TYPE_REQUEST:
case TYPE_RENEW:
if (!server_id ||
memcmp(&resp.server_id, server_id, sizeof(resp.server_id)))
return -1;
/* Falls through */
case TYPE_CONFIRM:
if (mh->type == TYPE_CONFIRM && server_id)
return -1;
if ((bad_ia = dhcpv6_ia_notonlink(p, &c->ip6.addr))) {
info("DHCPv6: received CONFIRM with inappropriate IA,"
" sending NotOnLink status in REPLY");
bad_ia->l = htons(OPT_VSIZE(ia_na) +
sizeof(sc_not_on_link));
n = sizeof(struct opt_ia_na);
memcpy(resp_not_on_link.var, bad_ia, n);
memcpy(resp_not_on_link.var + n,
&sc_not_on_link, sizeof(sc_not_on_link));
n += sizeof(sc_not_on_link);
memcpy(resp_not_on_link.var + n, client_id,
sizeof(struct opt_hdr) + ntohs(client_id->l));
n += sizeof(struct opt_hdr) + ntohs(client_id->l);
n = offsetof(struct resp_not_on_link_t, var) + n;
resp_not_on_link.uh.len = htons(n);
resp_not_on_link.hdr.xid = mh->xid;
tap_ip_send(c, src, IPPROTO_UDP,
(char *)&resp_not_on_link, n, mh->xid);
return 1;
}
info("DHCPv6: received REQUEST/RENEW/CONFIRM, sending REPLY");
break;
case TYPE_INFORMATION_REQUEST:
if (server_id &&
memcmp(&resp.server_id, server_id, sizeof(resp.server_id)))
return -1;
if (ia || dhcpv6_opt(p, &(size_t){ 0 }, OPT_IA_TA))
return -1;
info("DHCPv6: received INFORMATION_REQUEST, sending REPLY");
break;
case TYPE_REBIND:
if (!server_id ||
memcmp(&resp.server_id, server_id, sizeof(resp.server_id)))
return -1;
info("DHCPv6: received REBIND, sending REPLY");
break;
case TYPE_SOLICIT:
if (server_id)
return -1;
resp.hdr.type = TYPE_ADVERTISE;
info("DHCPv6: received SOLICIT, sending ADVERTISE");
break;
default:
return -1;
}
if (ia)
resp.ia_na.iaid = ((struct opt_ia_na *)ia)->iaid;
memcpy(&resp.client_id, client_id,
ntohs(client_id->l) + sizeof(struct opt_hdr));
n = offsetof(struct resp_t, client_id) +
sizeof(struct opt_hdr) + ntohs(client_id->l);
n = dhcpv6_dns_fill(c, (char *)&resp, n);
resp.uh.len = htons(n);
resp.hdr.xid = mh->xid;
tap_ip_send(c, src, IPPROTO_UDP, (char *)&resp, n, mh->xid);
c->ip6.addr_seen = c->ip6.addr;
return 1;
}
/**
* dhcpv6_init() - Initialise DUID and addresses for DHCPv6 server
* @c: Execution context
*/
void dhcpv6_init(const struct ctx *c)
{
time_t y2k = 946684800; /* Epoch to 2000-01-01T00:00:00Z, no mktime() */
uint32_t duid_time;
duid_time = htonl(difftime(time(NULL), y2k));
resp.server_id.duid_time = duid_time;
resp_not_on_link.server_id.duid_time = duid_time;
memcpy(resp.server_id.duid_lladdr, c->mac, sizeof(c->mac));
memcpy(resp_not_on_link.server_id.duid_lladdr, c->mac, sizeof(c->mac));
resp.ia_addr.addr = c->ip6.addr;
}
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