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passt/netlink.c
Stefano Brivio fde8004ab0 netlink: Use 8 KiB * netlink message header size as response buffer 
...instead of BUFSIZ. On musl, BUFSIZ is 1024, so we'll typically
truncate the response to the request we send in nl_link(). It's
usually 8192 or more with glibc.

There doesn't seem to be any macro defining the rtnetlink maximum
message size, and iproute2 just hardcodes 1024 * 1024 for the receive
buffer, but the example in netlink(7) makes somewhat sense, looking
at the kernel implementation.

It's not very clean, but we're very unlikely to hit that limit,
and if we do, we'll find out painlessly, because NLA_OK() will tell
us right away.

Reported-by: Chris Kuhn <kuhnchris+passt@kuhnchris.eu>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
2023-03-09 03:44:21 +01:00

507 lines
12 KiB
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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
*
* netlink.c - rtnetlink routines: interfaces, addresses, routes
*
* Copyright (c) 2020-2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*/
#include <sched.h>
#include <string.h>
#include <stddef.h>
#include <errno.h>
#include <sys/types.h>
#include <limits.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include "util.h"
#include "passt.h"
#include "log.h"
#include "netlink.h"
#define NLBUFSIZ (8192 * sizeof(struct nlmsghdr)) /* See netlink(7) */
/* Socket in init, in target namespace, sequence (just needs to be monotonic) */
static int nl_sock = -1;
static int nl_sock_ns = -1;
static int nl_seq;
/**
* nl_sock_init_do() - Set up netlink sockets in init or target namespace
* @arg: Execution context, if running from namespace, NULL otherwise
*
* Return: 0
*/
static int nl_sock_init_do(void *arg)
{
struct sockaddr_nl addr = { .nl_family = AF_NETLINK, };
int *s = arg ? &nl_sock_ns : &nl_sock;
#ifdef NETLINK_GET_STRICT_CHK
int y = 1;
#endif
if (arg)
ns_enter((struct ctx *)arg);
*s = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
if (*s < 0 || bind(*s, (struct sockaddr *)&addr, sizeof(addr))) {
*s = -1;
return 0;
}
#ifdef NETLINK_GET_STRICT_CHK
if (setsockopt(*s, SOL_NETLINK, NETLINK_GET_STRICT_CHK, &y, sizeof(y)))
debug("netlink: cannot set NETLINK_GET_STRICT_CHK on %i", *s);
#endif
return 0;
}
/**
* nl_sock_init() - Call nl_sock_init_do(), won't return on failure
* @c: Execution context
* @ns: Get socket in namespace, not in init
*/
void nl_sock_init(const struct ctx *c, bool ns)
{
if (ns) {
NS_CALL(nl_sock_init_do, c);
if (nl_sock_ns == -1)
goto fail;
} else {
nl_sock_init_do(NULL);
}
if (nl_sock == -1)
goto fail;
return;
fail:
die("Failed to get netlink socket");
}
/**
* nl_req() - Send netlink request and read response
* @ns: Use netlink socket in namespace
* @buf: Buffer for response (at least BUFSIZ long)
* @req: Request with netlink header
* @len: Request length
*
* Return: received length on success, negative error code on failure
*/
static int nl_req(int ns, char *buf, const void *req, ssize_t len)
{
int s = ns ? nl_sock_ns : nl_sock, done = 0;
char flush[NLBUFSIZ];
ssize_t n;
while (!done && (n = recv(s, flush, sizeof(flush), MSG_DONTWAIT)) > 0) {
struct nlmsghdr *nh = (struct nlmsghdr *)flush;
size_t nm = n;
for ( ; NLMSG_OK(nh, nm); nh = NLMSG_NEXT(nh, nm)) {
if (nh->nlmsg_type == NLMSG_DONE ||
nh->nlmsg_type == NLMSG_ERROR) {
done = 1;
break;
}
}
}
if ((send(s, req, len, 0) < len) ||
(len = recv(s, buf, NLBUFSIZ, 0)) < 0)
return -errno;
return len;
}
/**
* nl_get_ext_if() - Get interface index supporting IP version being probed
* @af: Address family (AF_INET or AF_INET6) to look for connectivity
* for.
*
* Return: interface index, 0 if not found
*/
unsigned int nl_get_ext_if(sa_family_t af)
{
struct { struct nlmsghdr nlh; struct rtmsg rtm; } req = {
.nlh.nlmsg_type = RTM_GETROUTE,
.nlh.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP,
.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)),
.nlh.nlmsg_seq = nl_seq++,
.rtm.rtm_table = RT_TABLE_MAIN,
.rtm.rtm_scope = RT_SCOPE_UNIVERSE,
.rtm.rtm_type = RTN_UNICAST,
.rtm.rtm_family = af,
};
struct nlmsghdr *nh;
struct rtattr *rta;
char buf[NLBUFSIZ];
ssize_t n;
size_t na;
if ((n = nl_req(0, buf, &req, sizeof(req))) < 0)
return 0;
nh = (struct nlmsghdr *)buf;
for ( ; NLMSG_OK(nh, n); nh = NLMSG_NEXT(nh, n)) {
struct rtmsg *rtm = (struct rtmsg *)NLMSG_DATA(nh);
if (rtm->rtm_dst_len || rtm->rtm_family != af)
continue;
for (rta = RTM_RTA(rtm), na = RTM_PAYLOAD(nh); RTA_OK(rta, na);
rta = RTA_NEXT(rta, na)) {
unsigned int ifi;
if (rta->rta_type != RTA_OIF)
continue;
ifi = *(unsigned int *)RTA_DATA(rta);
return ifi;
}
}
return 0;
}
/**
* nl_route() - Get/set default gateway for given interface and address family
* @ns: Use netlink socket in namespace
* @ifi: Interface index
* @af: Address family
* @gw: Default gateway to fill if zero, to set if not
*/
void nl_route(int ns, unsigned int ifi, sa_family_t af, void *gw)
{
int set = (af == AF_INET6 && !IN6_IS_ADDR_UNSPECIFIED(gw)) ||
(af == AF_INET && *(uint32_t *)gw);
struct req_t {
struct nlmsghdr nlh;
struct rtmsg rtm;
struct rtattr rta;
unsigned int ifi;
union {
struct {
struct rtattr rta_dst;
struct in6_addr d;
struct rtattr rta_gw;
struct in6_addr a;
} r6;
struct {
struct rtattr rta_dst;
uint32_t d;
struct rtattr rta_gw;
uint32_t a;
} r4;
} set;
} req = {
.nlh.nlmsg_type = set ? RTM_NEWROUTE : RTM_GETROUTE,
.nlh.nlmsg_flags = NLM_F_REQUEST,
.nlh.nlmsg_seq = nl_seq++,
.rtm.rtm_family = af,
.rtm.rtm_table = RT_TABLE_MAIN,
.rtm.rtm_scope = RT_SCOPE_UNIVERSE,
.rtm.rtm_type = RTN_UNICAST,
.rta.rta_type = RTA_OIF,
.rta.rta_len = RTA_LENGTH(sizeof(unsigned int)),
.ifi = ifi,
};
struct nlmsghdr *nh;
struct rtattr *rta;
struct rtmsg *rtm;
char buf[NLBUFSIZ];
ssize_t n;
size_t na;
if (set) {
if (af == AF_INET6) {
size_t rta_len = RTA_LENGTH(sizeof(req.set.r6.d));
req.nlh.nlmsg_len = offsetof(struct req_t, set.r6)
+ sizeof(req.set.r6);
req.set.r6.rta_dst.rta_type = RTA_DST;
req.set.r6.rta_dst.rta_len = rta_len;
memcpy(&req.set.r6.a, gw, sizeof(req.set.r6.a));
req.set.r6.rta_gw.rta_type = RTA_GATEWAY;
req.set.r6.rta_gw.rta_len = rta_len;
} else {
size_t rta_len = RTA_LENGTH(sizeof(req.set.r4.d));
req.nlh.nlmsg_len = offsetof(struct req_t, set.r4)
+ sizeof(req.set.r4);
req.set.r4.rta_dst.rta_type = RTA_DST;
req.set.r4.rta_dst.rta_len = rta_len;
req.set.r4.a = *(uint32_t *)gw;
req.set.r4.rta_gw.rta_type = RTA_GATEWAY;
req.set.r4.rta_gw.rta_len = rta_len;
}
req.rtm.rtm_protocol = RTPROT_BOOT;
req.nlh.nlmsg_flags |= NLM_F_ACK | NLM_F_EXCL | NLM_F_CREATE;
} else {
req.nlh.nlmsg_len = offsetof(struct req_t, set.r6);
req.nlh.nlmsg_flags |= NLM_F_DUMP;
}
if ((n = nl_req(ns, buf, &req, req.nlh.nlmsg_len)) < 0 || set)
return;
nh = (struct nlmsghdr *)buf;
for ( ; NLMSG_OK(nh, n); nh = NLMSG_NEXT(nh, n)) {
if (nh->nlmsg_type != RTM_NEWROUTE)
goto next;
rtm = (struct rtmsg *)NLMSG_DATA(nh);
if (rtm->rtm_dst_len)
continue;
for (rta = RTM_RTA(rtm), na = RTM_PAYLOAD(nh); RTA_OK(rta, na);
rta = RTA_NEXT(rta, na)) {
if (rta->rta_type != RTA_GATEWAY)
continue;
memcpy(gw, RTA_DATA(rta), RTA_PAYLOAD(rta));
return;
}
next:
if (nh->nlmsg_type == NLMSG_DONE)
break;
}
}
/**
* nl_addr() - Get/set IP addresses
* @ns: Use netlink socket in namespace
* @ifi: Interface index
* @af: Address family
* @addr: Global address to fill if zero, to set if not, ignored if NULL
* @prefix_len: Mask or prefix length, set or fetched (for IPv4)
* @addr_l: Link-scoped address to fill, NULL if not requested
*/
void nl_addr(int ns, unsigned int ifi, sa_family_t af,
void *addr, int *prefix_len, void *addr_l)
{
int set = addr && ((af == AF_INET6 && !IN6_IS_ADDR_UNSPECIFIED(addr)) ||
(af == AF_INET && *(uint32_t *)addr));
struct req_t {
struct nlmsghdr nlh;
struct ifaddrmsg ifa;
union {
struct {
struct rtattr rta_l;
uint32_t l;
struct rtattr rta_a;
uint32_t a;
} a4;
struct {
struct rtattr rta_l;
struct in6_addr l;
struct rtattr rta_a;
struct in6_addr a;
} a6;
} set;
} req = {
.nlh.nlmsg_type = set ? RTM_NEWADDR : RTM_GETADDR,
.nlh.nlmsg_flags = NLM_F_REQUEST,
.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg)),
.nlh.nlmsg_seq = nl_seq++,
.ifa.ifa_family = af,
.ifa.ifa_index = ifi,
.ifa.ifa_prefixlen = *prefix_len,
};
struct ifaddrmsg *ifa;
struct nlmsghdr *nh;
struct rtattr *rta;
char buf[NLBUFSIZ];
ssize_t n;
size_t na;
if (set) {
if (af == AF_INET6) {
size_t rta_len = RTA_LENGTH(sizeof(req.set.a6.l));
/* By default, strictly speaking, it's duplicated */
req.ifa.ifa_flags = IFA_F_NODAD;
req.nlh.nlmsg_len = offsetof(struct req_t, set.a6)
+ sizeof(req.set.a6);
memcpy(&req.set.a6.l, addr, sizeof(req.set.a6.l));
req.set.a6.rta_l.rta_len = rta_len;
req.set.a4.rta_l.rta_type = IFA_LOCAL;
memcpy(&req.set.a6.a, addr, sizeof(req.set.a6.a));
req.set.a6.rta_a.rta_len = rta_len;
req.set.a6.rta_a.rta_type = IFA_ADDRESS;
} else {
size_t rta_len = RTA_LENGTH(sizeof(req.set.a4.l));
req.nlh.nlmsg_len = offsetof(struct req_t, set.a4)
+ sizeof(req.set.a4);
req.set.a4.l = req.set.a4.a = *(uint32_t *)addr;
req.set.a4.rta_l.rta_len = rta_len;
req.set.a4.rta_l.rta_type = IFA_LOCAL;
req.set.a4.rta_a.rta_len = rta_len;
req.set.a4.rta_a.rta_type = IFA_ADDRESS;
}
req.ifa.ifa_scope = RT_SCOPE_UNIVERSE;
req.nlh.nlmsg_flags |= NLM_F_CREATE | NLM_F_ACK | NLM_F_EXCL;
} else {
req.nlh.nlmsg_flags |= NLM_F_DUMP;
}
if ((n = nl_req(ns, buf, &req, req.nlh.nlmsg_len)) < 0 || set)
return;
nh = (struct nlmsghdr *)buf;
for ( ; NLMSG_OK(nh, n); nh = NLMSG_NEXT(nh, n)) {
if (nh->nlmsg_type != RTM_NEWADDR)
goto next;
ifa = (struct ifaddrmsg *)NLMSG_DATA(nh);
if (ifa->ifa_index != ifi)
goto next;
for (rta = IFA_RTA(ifa), na = RTM_PAYLOAD(nh); RTA_OK(rta, na);
rta = RTA_NEXT(rta, na)) {
if (rta->rta_type != IFA_ADDRESS)
continue;
if (af == AF_INET && addr && !*(uint32_t *)addr) {
memcpy(addr, RTA_DATA(rta), RTA_PAYLOAD(rta));
*prefix_len = ifa->ifa_prefixlen;
} else if (af == AF_INET6 && addr &&
ifa->ifa_scope == RT_SCOPE_UNIVERSE &&
IN6_IS_ADDR_UNSPECIFIED(addr)) {
memcpy(addr, RTA_DATA(rta), RTA_PAYLOAD(rta));
}
if (addr_l &&
af == AF_INET6 && ifa->ifa_scope == RT_SCOPE_LINK &&
IN6_IS_ADDR_UNSPECIFIED(addr_l))
memcpy(addr_l, RTA_DATA(rta), RTA_PAYLOAD(rta));
}
next:
if (nh->nlmsg_type == NLMSG_DONE)
break;
}
}
/**
* nl_link() - Get/set link attributes
* @ns: Use netlink socket in namespace
* @ifi: Interface index
* @mac: MAC address to fill, if passed as zero, to set otherwise
* @up: If set, bring up the link
* @mtu: If non-zero, set interface MTU
*/
void nl_link(int ns, unsigned int ifi, void *mac, int up, int mtu)
{
int change = !MAC_IS_ZERO(mac) || up || mtu;
struct req_t {
struct nlmsghdr nlh;
struct ifinfomsg ifm;
struct rtattr rta;
union {
unsigned char mac[ETH_ALEN];
struct {
unsigned int mtu;
} mtu;
} set;
} req = {
.nlh.nlmsg_type = change ? RTM_NEWLINK : RTM_GETLINK,
.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
.nlh.nlmsg_flags = NLM_F_REQUEST | (change ? NLM_F_ACK : 0),
.nlh.nlmsg_seq = nl_seq++,
.ifm.ifi_family = AF_UNSPEC,
.ifm.ifi_index = ifi,
.ifm.ifi_flags = up ? IFF_UP : 0,
.ifm.ifi_change = up ? IFF_UP : 0,
};
struct ifinfomsg *ifm;
struct nlmsghdr *nh;
struct rtattr *rta;
char buf[NLBUFSIZ];
ssize_t n;
size_t na;
if (!MAC_IS_ZERO(mac)) {
req.nlh.nlmsg_len = sizeof(req);
memcpy(req.set.mac, mac, ETH_ALEN);
req.rta.rta_type = IFLA_ADDRESS;
req.rta.rta_len = RTA_LENGTH(ETH_ALEN);
if (nl_req(ns, buf, &req, req.nlh.nlmsg_len) < 0)
return;
up = 0;
}
if (mtu) {
req.nlh.nlmsg_len = offsetof(struct req_t, set.mtu)
+ sizeof(req.set.mtu);
req.set.mtu.mtu = mtu;
req.rta.rta_type = IFLA_MTU;
req.rta.rta_len = RTA_LENGTH(sizeof(unsigned int));
if (nl_req(ns, buf, &req, req.nlh.nlmsg_len) < 0)
return;
up = 0;
}
if (up && nl_req(ns, buf, &req, req.nlh.nlmsg_len) < 0)
return;
if (change)
return;
if ((n = nl_req(ns, buf, &req, req.nlh.nlmsg_len)) < 0)
return;
nh = (struct nlmsghdr *)buf;
for ( ; NLMSG_OK(nh, n); nh = NLMSG_NEXT(nh, n)) {
if (nh->nlmsg_type != RTM_NEWLINK)
goto next;
ifm = (struct ifinfomsg *)NLMSG_DATA(nh);
for (rta = IFLA_RTA(ifm), na = RTM_PAYLOAD(nh); RTA_OK(rta, na);
rta = RTA_NEXT(rta, na)) {
if (rta->rta_type != IFLA_ADDRESS)
continue;
memcpy(mac, RTA_DATA(rta), ETH_ALEN);
break;
}
next:
if (nh->nlmsg_type == NLMSG_DONE)
break;
}
}
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