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Don't create 'tap' socket for ports that are bound to loopback only

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If the user specifies an explicit loopback address for a port
binding, we're going to use that address for the 'tap' socket, and
the same exact address for the 'spliced' socket (because those are,
by definition, only bound to loopback addresses).

This means that the second binding will fail, and, unexpectedly, the
port is forwarded, but via tap device, which means the source address
in the namespace won't be a loopback address.

Make it explicit under which conditions we're creating which kind of
socket, by refactoring tcp_sock_init() into two separate functions
for IPv4 and IPv6 and gathering those conditions at the beginning.

Also, don't create spliced sockets if the user specifies explicitly
a non-loopback address, those are harmless but not desired either.

Fixes: 3c6ae62510 ("conf, tcp, udp: Allow address specification for forwarded ports")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Stefano Brivio 2022-10-12 16:48:52 +02:00
parent d0dd0242a6
commit 6f3e38cac5
2 changed files with 140 additions and 92 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

123
tcp.c
View file

@ -275,6 +275,7 @@
#include <netinet/in.h> #include <netinet/in.h>
#include <netinet/ip.h> #include <netinet/ip.h>
#include <stdint.h> #include <stdint.h>
#include <stdbool.h>
#include <stddef.h> #include <stddef.h>
#include <string.h> #include <string.h>
#include <sys/epoll.h> #include <sys/epoll.h>
@ -2906,8 +2907,8 @@ static void tcp_conn_from_sock(struct ctx *c, union epoll_ref ref,
memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero)); memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero));
memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one)); memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one));
if (s_addr >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET || if (IPV4_IS_LOOPBACK(s_addr) || s_addr == INADDR_ANY ||
s_addr == INADDR_ANY || htonl(s_addr) == c->ip4.addr_seen) htonl(s_addr) == c->ip4.addr_seen)
s_addr = ntohl(c->ip4.gw); s_addr = ntohl(c->ip4.gw);
s_addr = htonl(s_addr); s_addr = htonl(s_addr);
@ -3073,38 +3074,39 @@ void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events,
} }
/** /**
* tcp_sock_init() - Initialise listening sockets for a given port * tcp_sock_init4() - Initialise listening sockets for a given IPv4 port
* @c: Execution context * @c: Execution context
* @ns: In pasta mode, if set, bind with loopback address in namespace * @ns: In pasta mode, if set, bind with loopback address in namespace
* @af: Address family to select a specific IP version, or AF_UNSPEC
* @addr: Pointer to address for binding, NULL if not configured * @addr: Pointer to address for binding, NULL if not configured
* @ifname: Name of interface to bind to, NULL if not configured * @ifname: Name of interface to bind to, NULL if not configured
* @port: Port, host order * @port: Port, host order
*/ */
void tcp_sock_init(const struct ctx *c, int ns, sa_family_t af, static void tcp_sock_init4(const struct ctx *c, int ns, const in_addr_t *addr,
const void *addr, const char *ifname, in_port_t port) const char *ifname, in_port_t port)
{ {
union tcp_epoll_ref tref = { .tcp.listen = 1, .tcp.outbound = ns }; union tcp_epoll_ref tref = { .tcp.listen = 1, .tcp.outbound = ns };
const void *bind_addr; bool spliced = false, tap = true;
int s; int s;
if (c->mode == MODE_PASTA) {
spliced = !addr ||
ntohl(*addr) == INADDR_ANY ||
IPV4_IS_LOOPBACK(ntohl(*addr));
if (!addr)
addr = &c->ip4.addr;
tap = !ns && !IPV4_IS_LOOPBACK(ntohl(*addr));
}
if (ns) if (ns)
tref.tcp.index = (in_port_t)(port + c->tcp.fwd_out.delta[port]); tref.tcp.index = (in_port_t)(port + c->tcp.fwd_out.delta[port]);
else else
tref.tcp.index = (in_port_t)(port + c->tcp.fwd_in.delta[port]); tref.tcp.index = (in_port_t)(port + c->tcp.fwd_in.delta[port]);
if (af == AF_INET || af == AF_UNSPEC) { if (tap) {
if (!addr && c->mode == MODE_PASTA) s = sock_l4(c, AF_INET, IPPROTO_TCP, addr, ifname, port,
bind_addr = &c->ip4.addr; tref.u32);
else
bind_addr = addr;
tref.tcp.v6 = 0;
tref.tcp.splice = 0;
if (!ns) {
s = sock_l4(c, AF_INET, IPPROTO_TCP, bind_addr, ifname,
port, tref.u32);
if (s >= 0) if (s >= 0)
tcp_sock_set_bufsize(c, s); tcp_sock_set_bufsize(c, s);
else else
@ -3114,12 +3116,13 @@ void tcp_sock_init(const struct ctx *c, int ns, sa_family_t af,
tcp_sock_init_ext[port][V4] = s; tcp_sock_init_ext[port][V4] = s;
} }
if (c->mode == MODE_PASTA) { if (spliced) {
bind_addr = &(uint32_t){ htonl(INADDR_LOOPBACK) };
tref.tcp.splice = 1; tref.tcp.splice = 1;
s = sock_l4(c, AF_INET, IPPROTO_TCP, bind_addr, ifname,
port, tref.u32); addr = &(uint32_t){ htonl(INADDR_LOOPBACK) };
s = sock_l4(c, AF_INET, IPPROTO_TCP, addr, ifname, port,
tref.u32);
if (s >= 0) if (s >= 0)
tcp_sock_set_bufsize(c, s); tcp_sock_set_bufsize(c, s);
else else
@ -3134,18 +3137,42 @@ void tcp_sock_init(const struct ctx *c, int ns, sa_family_t af,
} }
} }
if (af == AF_INET6 || af == AF_UNSPEC) { /**
if (!addr && c->mode == MODE_PASTA) * tcp_sock_init6() - Initialise listening sockets for a given IPv6 port
bind_addr = &c->ip6.addr; * @c: Execution context
* @ns: In pasta mode, if set, bind with loopback address in namespace
* @addr: Pointer to address for binding, NULL if not configured
* @ifname: Name of interface to bind to, NULL if not configured
* @port: Port, host order
*/
static void tcp_sock_init6(const struct ctx *c, int ns,
const struct in6_addr *addr, const char *ifname,
in_port_t port)
{
union tcp_epoll_ref tref = { .tcp.listen = 1, .tcp.outbound = ns,
.tcp.v6 = 1 };
bool spliced = false, tap = true;
int s;
if (c->mode == MODE_PASTA) {
spliced = !addr ||
IN6_IS_ADDR_UNSPECIFIED(addr) ||
IN6_IS_ADDR_LOOPBACK(addr);
if (!addr)
addr = &c->ip6.addr;
tap = !ns && !IN6_IS_ADDR_LOOPBACK(addr);
}
if (ns)
tref.tcp.index = (in_port_t)(port + c->tcp.fwd_out.delta[port]);
else else
bind_addr = addr; tref.tcp.index = (in_port_t)(port + c->tcp.fwd_in.delta[port]);
tref.tcp.v6 = 1; if (tap) {
s = sock_l4(c, AF_INET6, IPPROTO_TCP, addr, ifname, port,
tref.tcp.splice = 0; tref.u32);
if (!ns) {
s = sock_l4(c, AF_INET6, IPPROTO_TCP, bind_addr, ifname,
port, tref.u32);
if (s >= 0) if (s >= 0)
tcp_sock_set_bufsize(c, s); tcp_sock_set_bufsize(c, s);
else else
@ -3155,12 +3182,13 @@ void tcp_sock_init(const struct ctx *c, int ns, sa_family_t af,
tcp_sock_init_ext[port][V6] = s; tcp_sock_init_ext[port][V6] = s;
} }
if (c->mode == MODE_PASTA) { if (spliced) {
bind_addr = &in6addr_loopback;
tref.tcp.splice = 1; tref.tcp.splice = 1;
s = sock_l4(c, AF_INET6, IPPROTO_TCP, bind_addr, ifname,
port, tref.u32); addr = &in6addr_loopback;
s = sock_l4(c, AF_INET6, IPPROTO_TCP, addr, ifname, port,
tref.u32);
if (s >= 0) if (s >= 0)
tcp_sock_set_bufsize(c, s); tcp_sock_set_bufsize(c, s);
else else
@ -3174,6 +3202,23 @@ void tcp_sock_init(const struct ctx *c, int ns, sa_family_t af,
} }
} }
} }
/**
* tcp_sock_init() - Initialise listening sockets for a given port
* @c: Execution context
* @ns: In pasta mode, if set, bind with loopback address in namespace
* @af: Address family to select a specific IP version, or AF_UNSPEC
* @addr: Pointer to address for binding, NULL if not configured
* @ifname: Name of interface to bind to, NULL if not configured
* @port: Port, host order
*/
void tcp_sock_init(const struct ctx *c, int ns, sa_family_t af,
const void *addr, const char *ifname, in_port_t port)
{
if (af == AF_INET || af == AF_UNSPEC)
tcp_sock_init4(c, ns, addr, ifname, port);
if (af == AF_INET6 || af == AF_UNSPEC)
tcp_sock_init6(c, ns, addr, ifname, port);
} }
/** /**

3
util.h
View file

@ -81,6 +81,9 @@
#define MAC_ZERO ((uint8_t [ETH_ALEN]){ 0 }) #define MAC_ZERO ((uint8_t [ETH_ALEN]){ 0 })
#define MAC_IS_ZERO(addr) (!memcmp((addr), MAC_ZERO, ETH_ALEN)) #define MAC_IS_ZERO(addr) (!memcmp((addr), MAC_ZERO, ETH_ALEN))
#define IPV4_IS_LOOPBACK(addr) \
((addr) >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET)
#define NS_FN_STACK_SIZE (RLIMIT_STACK_VAL * 1024 / 4) #define NS_FN_STACK_SIZE (RLIMIT_STACK_VAL * 1024 / 4)
#define NS_CALL(fn, arg) \ #define NS_CALL(fn, arg) \
do { \ do { \