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passt/ndp.c
David Gibson 975cfa5f32 Initialise our_tap_ll to ip6.gw when suitable 
In every place we use our_tap_ll, we only use it as a fallback if the
IPv6 gateway address is not link-local.  We can avoid that conditional at
use time by doing it at initialisation of our_tap_ll instead.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
2024-08-21 12:00:22 +02:00

355 lines
7.7 KiB
C
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// SPDX-License-Identifier: GPL-2.0-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
*
* ndp.c - NDP support for PASST
*
* Copyright (c) 2020-2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*
*/
#include <stdio.h>
#include <stddef.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/ip.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/if_ether.h>
#include <linux/icmpv6.h>
#include "checksum.h"
#include "util.h"
#include "ip.h"
#include "passt.h"
#include "tap.h"
#include "log.h"
#define RS 133
#define RA 134
#define NS 135
#define NA 136
enum ndp_option_types {
OPT_SRC_L2_ADDR = 1,
OPT_TARGET_L2_ADDR = 2,
OPT_PREFIX_INFO = 3,
OPT_MTU = 5,
OPT_RDNSS_TYPE = 25,
OPT_DNSSL_TYPE = 31,
};
/**
* struct opt_header - Option header
* @type: Option type
* @len: Option length, in units of 8 bytes
*/
struct opt_header {
uint8_t type;
uint8_t len;
} __attribute__((packed));
/**
* struct opt_l2_addr - Link-layer address
* @header: Option header
* @mac: MAC address
*/
struct opt_l2_addr {
struct opt_header header;
unsigned char mac[ETH_ALEN];
} __attribute__((packed));
/**
* struct ndp_na - NDP Neighbor Advertisement (NA) message
* @ih: ICMPv6 header
* @target_addr: Target IPv6 address
* @target_l2_addr: Target link-layer address
*/
struct ndp_na {
struct icmp6hdr ih;
struct in6_addr target_addr;
struct opt_l2_addr target_l2_addr;
} __attribute__((packed));
/**
* struct opt_prefix_info - Prefix Information option
* @header: Option header
* @prefix_len: The number of leading bits in the Prefix that are valid
* @prefix_flags: Flags associated with the prefix
* @valid_lifetime: Valid lifetime (ms)
* @pref_lifetime: Preferred lifetime (ms)
* @reserved: Unused
*/
struct opt_prefix_info {
struct opt_header header;
uint8_t prefix_len;
uint8_t prefix_flags;
uint32_t valid_lifetime;
uint32_t pref_lifetime;
uint32_t reserved;
} __attribute__((packed));
/**
* struct opt_mtu - Maximum transmission unit (MTU) option
* @header: Option header
* @reserved: Unused
* @value: MTU value, network order
*/
struct opt_mtu {
struct opt_header header;
uint16_t reserved;
uint32_t value;
} __attribute__((packed));
/**
* struct rdnss - Recursive DNS Server (RDNSS) option
* @header: Option header
* @reserved: Unused
* @lifetime: Validity time (s)
* @dns: List of DNS server addresses
*/
struct opt_rdnss {
struct opt_header header;
uint16_t reserved;
uint32_t lifetime;
struct in6_addr dns[MAXNS + 1];
} __attribute__((packed));
/**
* struct dnssl - DNS Search List (DNSSL) option
* @header: Option header
* @reserved: Unused
* @lifetime: Validity time (s)
* @domains: List of NULL-seperated search domains
*/
struct opt_dnssl {
struct opt_header header;
uint16_t reserved;
uint32_t lifetime;
unsigned char domains[MAXDNSRCH * NS_MAXDNAME];
} __attribute__((packed));
/**
* struct ndp_ra - NDP Router Advertisement (RA) message
* @ih: ICMPv6 header
* @reachable: Reachability time, after confirmation (ms)
* @retrans: Time between retransmitted NS messages (ms)
* @prefix_info: Prefix Information option
* @prefix: IPv6 prefix
* @mtu: MTU option
* @source_ll: Target link-layer address
* @var: Variable fields
*/
struct ndp_ra {
struct icmp6hdr ih;
uint32_t reachable;
uint32_t retrans;
struct opt_prefix_info prefix_info;
struct in6_addr prefix;
struct opt_l2_addr source_ll;
unsigned char var[sizeof(struct opt_mtu) + sizeof(struct opt_rdnss) +
sizeof(struct opt_dnssl)];
} __attribute__((packed));
/**
* struct ndp_ns - NDP Neighbor Solicitation (NS) message
* @ih: ICMPv6 header
* @target_addr: Target IPv6 address
*/
struct ndp_ns {
struct icmp6hdr ih;
struct in6_addr target_addr;
} __attribute__((packed));
/**
* ndp() - Check for NDP solicitations, reply as needed
* @c: Execution context
* @ih: ICMPv6 header
* @saddr: Source IPv6 address
* @p: Packet pool
*
* Return: 0 if not handled here, 1 if handled, -1 on failure
*/
int ndp(struct ctx *c, const struct icmp6hdr *ih, const struct in6_addr *saddr,
const struct pool *p)
{
struct ndp_na na = {
.ih = {
.icmp6_type = NA,
.icmp6_code = 0,
.icmp6_router = 1,
.icmp6_solicited = 1,
.icmp6_override = 1,
},
.target_l2_addr = {
.header = {
.type = OPT_TARGET_L2_ADDR,
.len = 1,
},
}
};
struct ndp_ra ra = {
.ih = {
.icmp6_type = RA,
.icmp6_code = 0,
.icmp6_hop_limit = 255,
/* RFC 8319 */
.icmp6_rt_lifetime = htons_constant(65535),
.icmp6_addrconf_managed = 1,
},
.prefix_info = {
.header = {
.type = OPT_PREFIX_INFO,
.len = 4,
},
.prefix_len = 64,
.prefix_flags = 0xc0, /* prefix flags: L, A */
.valid_lifetime = ~0U,
.pref_lifetime = ~0U,
},
.source_ll = {
.header = {
.type = OPT_SRC_L2_ADDR,
.len = 1,
},
},
};
const struct in6_addr *rsaddr; /* src addr for reply */
unsigned char *ptr = NULL;
size_t dlen;
if (ih->icmp6_type < RS || ih->icmp6_type > NA)
return 0;
if (c->no_ndp)
return 1;
if (ih->icmp6_type == NS) {
struct ndp_ns *ns = packet_get(p, 0, 0, sizeof(struct ndp_ns),
NULL);
if (!ns)
return -1;
if (IN6_IS_ADDR_UNSPECIFIED(saddr))
return 1;
info("NDP: received NS, sending NA");
memcpy(&na.target_addr, &ns->target_addr,
sizeof(na.target_addr));
memcpy(na.target_l2_addr.mac, c->our_tap_mac, ETH_ALEN);
} else if (ih->icmp6_type == RS) {
size_t dns_s_len = 0;
int i, n;
if (c->no_ra)
return 1;
info("NDP: received RS, sending RA");
memcpy(&ra.prefix, &c->ip6.addr, sizeof(ra.prefix));
ptr = &ra.var[0];
if (c->mtu != -1) {
struct opt_mtu *mtu = (struct opt_mtu *)ptr;
*mtu = (struct opt_mtu) {
.header = {
.type = OPT_MTU,
.len = 1,
},
.value = htonl(c->mtu),
};
ptr += sizeof(struct opt_mtu);
}
if (c->no_dhcp_dns)
goto dns_done;
for (n = 0; !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns[n]); n++);
if (n) {
struct opt_rdnss *rdnss = (struct opt_rdnss *)ptr;
*rdnss = (struct opt_rdnss) {
.header = {
.type = OPT_RDNSS_TYPE,
.len = 1 + 2 * n,
},
.lifetime = ~0U,
};
for (i = 0; i < n; i++) {
memcpy(&rdnss->dns[i], &c->ip6.dns[i],
sizeof(rdnss->dns[i]));
}
ptr += offsetof(struct opt_rdnss, dns) +
i * sizeof(rdnss->dns[0]);
for (n = 0; *c->dns_search[n].n; n++)
dns_s_len += strlen(c->dns_search[n].n) + 2;
}
if (!c->no_dhcp_dns_search && dns_s_len) {
struct opt_dnssl *dnssl = (struct opt_dnssl *)ptr;
*dnssl = (struct opt_dnssl) {
.header = {
.type = OPT_DNSSL_TYPE,
.len = DIV_ROUND_UP(dns_s_len, 8) + 1,
},
.lifetime = ~0U,
};
ptr = dnssl->domains;
for (i = 0; i < n; i++) {
size_t len;
char *dot;
*(ptr++) = '.';
len = sizeof(dnssl->domains) -
(ptr - dnssl->domains);
strncpy((char *)ptr, c->dns_search[i].n, len);
for (dot = (char *)ptr - 1; *dot; dot++) {
if (*dot == '.')
*dot = strcspn(dot + 1, ".");
}
ptr += strlen(c->dns_search[i].n);
*(ptr++) = 0;
}
memset(ptr, 0, 8 - dns_s_len % 8); /* padding */
ptr += 8 - dns_s_len % 8;
}
dns_done:
memcpy(&ra.source_ll.mac, c->our_tap_mac, ETH_ALEN);
} else {
return 1;
}
if (IN6_IS_ADDR_LINKLOCAL(saddr))
c->ip6.addr_ll_seen = *saddr;
else
c->ip6.addr_seen = *saddr;
rsaddr = &c->ip6.our_tap_ll;
if (ih->icmp6_type == NS) {
dlen = sizeof(struct ndp_na);
tap_icmp6_send(c, rsaddr, saddr, &na, dlen);
} else if (ih->icmp6_type == RS) {
dlen = ptr - (unsigned char *)&ra;
tap_icmp6_send(c, rsaddr, saddr, &ra, dlen);
}
return 1;
}
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