[PATCH v2 3/8] flow: add mac address of LAN local remote hosts to flow

[Jon Maloy <jmaloy@redhat.com>]

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 flowside structure is a convenient
location for storing that address, so we do that in this commit.

Note that we don´t add usage of this address in this commit, - that
will come in later commits.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 flow.c | 13 ++++++++++++-
 flow.h |  2 ++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/flow.c b/flow.c
index da5c813..fffc817 100644
--- a/flow.c
+++ b/flow.c
@@ -20,6 +20,7 @@
 #include "flow.h"
 #include "flow_table.h"
 #include "repair.h"
+#include "netlink.h"
 
 const char *flow_state_str[] = {
 	[FLOW_STATE_FREE]	= "FREE",
@@ -438,7 +439,7 @@ struct flowside *flow_target(const struct ctx *c, union flow *flow,
 {
 	char estr[INANY_ADDRSTRLEN], fstr[INANY_ADDRSTRLEN];
 	struct flow_common *f = &flow->f;
-	const struct flowside *ini = &f->side[INISIDE];
+	struct flowside *ini = &f->side[INISIDE];
 	struct flowside *tgt = &f->side[TGTSIDE];
 	uint8_t tgtpif = PIF_NONE;
 
@@ -446,10 +447,16 @@ struct flowside *flow_target(const struct ctx *c, union flow *flow,
 	ASSERT(f->type == FLOW_TYPE_NONE);
 	ASSERT(f->pif[INISIDE] != PIF_NONE && f->pif[TGTSIDE] == PIF_NONE);
 	ASSERT(flow->f.state == FLOW_STATE_INI);
+	memcpy(ini->mac, c->our_tap_mac, ETH_ALEN);
+	memcpy(tgt->mac, c->our_tap_mac, ETH_ALEN);
 
 	switch (f->pif[INISIDE]) {
 	case PIF_TAP:
 		tgtpif = fwd_nat_from_tap(c, proto, ini, tgt);
+
+		/* If remote host on local network - insert its mac address */
+		if (!memcmp(&tgt->eaddr, &ini->oaddr, sizeof(ini->oaddr)))
+			nl_mac_get(nl_sock, &ini->oaddr, ini->mac);
 		break;
 
 	case PIF_SPLICE:
@@ -458,6 +465,10 @@ struct flowside *flow_target(const struct ctx *c, union flow *flow,
 
 	case PIF_HOST:
 		tgtpif = fwd_nat_from_host(c, proto, ini, tgt);
+
+		/* If remote host on local network - insert its mac address */
+		if (!memcmp(&tgt->oaddr, &ini->eaddr, sizeof(ini->eaddr)))
+			nl_mac_get(nl_sock, &tgt->oaddr, tgt->mac);
 		break;
 
 	default:
diff --git a/flow.h b/flow.h
index cac618a..916951b 100644
--- a/flow.h
+++ b/flow.h
@@ -143,12 +143,14 @@ extern const uint8_t flow_proto[];
  * @oaddr:	Our address (local address from passt's PoV)
  * @eport:	Endpoint port
  * @oport:	Our port
+ * @mac:	MAC address of remote endpoint
  */
 struct flowside {
 	union inany_addr	oaddr;
 	union inany_addr	eaddr;
 	in_port_t		oport;
 	in_port_t		eport;
+	unsigned char 		mac[6];
 };
 
 /**
-- 
@@ -143,12 +143,14 @@ extern const uint8_t flow_proto[];
  * @oaddr:	Our address (local address from passt's PoV)
  * @eport:	Endpoint port
  * @oport:	Our port
+ * @mac:	MAC address of remote endpoint
  */
 struct flowside {
 	union inany_addr	oaddr;
 	union inany_addr	eaddr;
 	in_port_t		oport;
 	in_port_t		eport;
+	unsigned char 		mac[6];
 };
 
 /**
-- 
2.48.1