flow: add MAC address of LAN local remote hosts to flow

When communicating with remote hosts on the local network, some guest
applications want to see the real MAC address of that host instead
of PASST/PASTA's own tap address. The flow_common structure is a
convenient location for storing that address, so we do that in this
commit.

Note that we don´t add actual usage of this address here, that will
be done in later commits.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

3 files changed, 6 insertions, 0 deletions

diff --git a/flow.c b/flow.c
index feefda3..a57d7b9 100644
--- a/flow.c
+++ b/flow.c
@@ -449,6 +449,7 @@ struct flowside *flow_target(const struct ctx *c, union flow *flow,
 
 	switch (f->pif[INISIDE]) {
 	case PIF_TAP:
+		memcpy(f->tap_omac, MAC_UNDEF, ETH_ALEN);
 		tgtpif = fwd_nat_from_tap(c, proto, ini, tgt);
 		break;
 
@@ -458,6 +459,7 @@ struct flowside *flow_target(const struct ctx *c, union flow *flow,
 
 	case PIF_HOST:
 		tgtpif = fwd_nat_from_host(c, proto, ini, tgt);
+		fwd_neigh_mac_get(c, &tgt->oaddr, f->tap_omac);
 		break;
 
 	default:
diff --git a/flow.h b/flow.h
index cac618a..f342895 100644
--- a/flow.h
+++ b/flow.h
@@ -177,6 +177,7 @@ int flowside_connect(const struct ctx *c, int s,
  * @type:	Type of packet flow
  * @pif[]:	Interface for each side of the flow
  * @side[]:	Information for each side of the flow
+ * @tap_omac: MAC address of remote endpoint as seen from the guest
  */
 struct flow_common {
 #ifdef __GNUC__
@@ -192,6 +193,7 @@ struct flow_common {
 #endif
 	uint8_t		pif[SIDES];
 	struct flowside	side[SIDES];
+	uint8_t		tap_omac[6];
 };
 
 #define FLOW_INDEX_BITS		17	/* 128k - 1 */
diff --git a/util.h b/util.h
index 22eaac5..6fc8f5d 100644
--- a/util.h
+++ b/util.h
@@ -101,6 +101,8 @@ void abort_with_msg(const char *fmt, ...)
 	((uint8_t [ETH_ALEN]){ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff })
 #define MAC_ZERO		((uint8_t [ETH_ALEN]){ 0 })
 #define MAC_IS_ZERO(addr)	(!memcmp((addr), MAC_ZERO, ETH_ALEN))
+#define MAC_UNDEF		MAC_BROADCAST
+#define MAC_IS_UNDEF(addr)	(!memcmp((addr), MAC_UNDEF, ETH_ALEN))
 
 #ifndef __bswap_constant_16
 #define __bswap_constant_16(x)						\