When we receive an ARP or NTP request over the tap interface for a
host on the local network, we respond with that host's real mac
address.
The local host, which is acting as a proxy for the default gateway,
is still exempted from this rule.
Signed-off-by: Jon Maloy
---
arp.c | 9 +++++++++
fwd.c | 2 +-
fwd.h | 3 ++-
ndp.c | 11 +++++++++++
4 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/arp.c b/arp.c
index fc482bb..fbd8219 100644
--- a/arp.c
+++ b/arp.c
@@ -29,6 +29,7 @@
#include "dhcp.h"
#include "passt.h"
#include "tap.h"
+#include "netlink.h"
/**
* arp() - Check if this is a supported ARP message, reply as needed
@@ -39,6 +40,8 @@
*/
int arp(const struct ctx *c, const struct pool *p)
{
+ union inany_addr translated;
+ union inany_addr addr;
unsigned char swap[4];
struct ethhdr *eh;
struct arphdr *ah;
@@ -72,6 +75,12 @@ int arp(const struct ctx *c, const struct pool *p)
memcpy(am->tha, am->sha, sizeof(am->tha));
memcpy(am->sha, c->our_tap_mac, sizeof(am->sha));
+ /* If remote host on local network - respond with its mac address */
+ inany_from_af(&addr, AF_INET, am->tip);
+ nat_outbound(c, &addr, &translated);
+ if (!memcmp(&addr, &translated, sizeof(addr)))
+ nl_mac_get(nl_sock, &addr, am->sha);
+
memcpy(swap, am->tip, sizeof(am->tip));
memcpy(am->tip, am->sip, sizeof(am->tip));
memcpy(am->sip, swap, sizeof(am->sip));
diff --git a/fwd.c b/fwd.c
index 250cf56..02ebc9d 100644
--- a/fwd.c
+++ b/fwd.c
@@ -332,7 +332,7 @@ static bool fwd_guest_accessible(const struct ctx *c,
* Only handles translations that depend *only* on the address. Anything
* related to specific ports or flows is handled elsewhere.
*/
-static void nat_outbound(const struct ctx *c, const union inany_addr *addr,
+void nat_outbound(const struct ctx *c, const union inany_addr *addr,
union inany_addr *translated)
{
if (inany_equals4(addr, &c->ip4.map_host_loopback))
diff --git a/fwd.h b/fwd.h
index 0458a3c..61632f2 100644
--- a/fwd.h
+++ b/fwd.h
@@ -56,5 +56,6 @@ uint8_t fwd_nat_from_splice(const struct ctx *c, uint8_t proto,
const struct flowside *ini, struct flowside *tgt);
uint8_t fwd_nat_from_host(const struct ctx *c, uint8_t proto,
const struct flowside *ini, struct flowside *tgt);
-
+void nat_outbound(const struct ctx *c, const union inany_addr *addr,
+ union inany_addr *translated);
#endif /* FWD_H */
diff --git a/ndp.c b/ndp.c
index 3e15494..d702f37 100644
--- a/ndp.c
+++ b/ndp.c
@@ -32,6 +32,7 @@
#include "passt.h"
#include "tap.h"
#include "log.h"
+#include "netlink.h"
#define RT_LIFETIME 65535
@@ -196,6 +197,9 @@ static void ndp_send(const struct ctx *c, const struct in6_addr *dst,
static void ndp_na(const struct ctx *c, const struct in6_addr *dst,
const struct in6_addr *addr)
{
+ union inany_addr translated;
+ union inany_addr addr_any;
+
struct ndp_na na = {
.ih = {
.icmp6_type = NA,
@@ -215,6 +219,13 @@ static void ndp_na(const struct ctx *c, const struct in6_addr *dst,
memcpy(na.target_l2_addr.mac, c->our_tap_mac, ETH_ALEN);
+ /* If remote host on local network - respond with its mac address */
+ inany_from_af(&addr_any, AF_INET6, addr);
+ nat_outbound(c, &addr_any, &translated);
+
+ if (!memcmp(&addr_any, &translated, sizeof(addr_any)))
+ nl_mac_get(nl_sock, &addr_any, na.target_l2_addr.mac);
+
ndp_send(c, dst, &na, sizeof(na));
}
--
2.48.1