Currently, outbound forwards (-T, -U) are handled by sockets bound to the
loopback address. Typically we create two sockets, one for 127.0.0.1 and
one for ::1.
This has some disadvantages:
* The guest can't connect via 127.0.0.0/8 addresses other than 127.0.0.1
* We can't use dual-stack sockets, we have to have separate sockets for
IPv4 and IPv6.
The restriction exists for a reason though. If the guest has any
interfaces other than pasta (e.g. a VPN tunnel) external hosts could reach
the host via the forwards. Especially combined with -T auto / -U auto this
would make it very easy to make a mistake with nasty security implications.
We can achieve this a different way, however. Don't bind to a specific
address, but _do_ use SO_BINDTODEVICE to restrict the sockets to the "lo"
interface.
Note that although traffic to a local but non-loopback address is passed
over the 'lo' interface (as seen by netfilter and dumpcap), it doesn't
count as attached to that interface for the purposes of SO_BINDTODEVICE
(information from the routing table overrides the "physical" interface).
So, this change doesn't help for bug 100.
It's also not a complete fix for bug 113, it does however:
* Get us a step closer to fixing bug 113
* Slightly simplify the code
* Make things a bit easier to allow more flexible binding on the guest in
in future
Link: https://bugs.passt.top/show_bug.cgi?id=100
Link: https://bugs.passt.top/show_bug.cgi?id=113
Signed-off-by: David Gibson
---
pif.c | 6 ------
tcp.c | 19 ++-----------------
udp.c | 10 +++-------
3 files changed, 5 insertions(+), 30 deletions(-)
diff --git a/pif.c b/pif.c
index 85904f35..db447b4f 100644
--- a/pif.c
+++ b/pif.c
@@ -81,12 +81,6 @@ int pif_sock_l4(const struct ctx *c, enum epoll_type type, uint8_t pif,
ASSERT(pif_is_socket(pif));
- if (pif == PIF_SPLICE) {
- /* Sanity checks */
- ASSERT(!ifname);
- ASSERT(addr && inany_is_loopback(addr));
- }
-
if (!addr) {
ref.fd = sock_l4_dualstack(c, type, port, ifname);
} else {
diff --git a/tcp.c b/tcp.c
index 2abb8be4..bd25952f 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2618,21 +2618,6 @@ int tcp_sock_init(const struct ctx *c, uint8_t pif,
return 0;
}
-/**
- * tcp_ns_sock_init() - Init socket to listen for spliced outbound connections
- * @c: Execution context
- * @port: Port, host order
- */
-static void tcp_ns_sock_init(const struct ctx *c, in_port_t port)
-{
- ASSERT(!c->no_tcp);
-
- if (c->ifi4)
- tcp_sock_init_one(c, PIF_SPLICE, &inany_loopback4, NULL, port);
- if (c->ifi6)
- tcp_sock_init_one(c, PIF_SPLICE, &inany_loopback6, NULL, port);
-}
-
/**
* tcp_ns_socks_init() - Bind sockets in namespace for outbound connections
* @arg: Execution context
@@ -2651,7 +2636,7 @@ static int tcp_ns_socks_init(void *arg)
if (!bitmap_isset(c->tcp.fwd_out.map, port))
continue;
- tcp_ns_sock_init(c, port);
+ tcp_sock_init(c, PIF_SPLICE, NULL, "lo", port);
}
return 0;
@@ -2826,7 +2811,7 @@ static void tcp_port_rebind(struct ctx *c, bool outbound)
if ((c->ifi4 && socks[port][V4] == -1) ||
(c->ifi6 && socks[port][V6] == -1)) {
if (outbound)
- tcp_ns_sock_init(c, port);
+ tcp_sock_init(c, PIF_SPLICE, NULL, "lo", port);
else
tcp_sock_init(c, PIF_HOST, NULL, NULL, port);
}
diff --git a/udp.c b/udp.c
index 3d097fbb..f3d445cf 100644
--- a/udp.c
+++ b/udp.c
@@ -1213,14 +1213,10 @@ static void udp_port_rebind(struct ctx *c, bool outbound)
if ((c->ifi4 && socks[V4][port] == -1) ||
(c->ifi6 && socks[V6][port] == -1)) {
- if (outbound) {
- udp_sock_init(c, PIF_SPLICE,
- &inany_loopback4, NULL, port);
- udp_sock_init(c, PIF_SPLICE,
- &inany_loopback6, NULL, port);
- } else {
+ if (outbound)
+ udp_sock_init(c, PIF_SPLICE, NULL, "lo", port);
+ else
udp_sock_init(c, PIF_HOST, NULL, NULL, port);
- }
}
}
}
--
2.51.1