slirp: Add out-of-band ethernet address

If a network card supports NC-SI, then it redirects all traffic with the
out-of-band (OOB) management controller's (MC) ethernet address to the
out-of-band management controller, usually over some sideband RMII
interface, not like the PCIe connection to the main host.

It's also pretty common for the network card to provision the out-of-band
management controller's ethernet address. At startup, the OOB MC asks the
network card what its MAC address is through OEM NC-SI commands. This
protocol is so common that it's going to be standardized soon in NC-SI 1.2.0
[1] as "Get MC MAC Address".

Note: At some point, the network card may provision *multiple* OOB ethernet
addresses, but right now everything just uses one.

[1] https://www.dmtf.org/sites/default/files/standards/documents/DSP0222_1.2.0WIP80.pdf

Signed-off-by: Peter Delevoryas <pdel@fb.com>

3 files changed, 8 insertions, 0 deletions

diff --git a/src/libslirp.h b/src/libslirp.h
index 35ddab6..3afad21 100644
--- a/src/libslirp.h
+++ b/src/libslirp.h
@@ -144,6 +144,11 @@ typedef struct SlirpConfig {
      * Fields introduced in SlirpConfig version 5 begin
      */
     uint32_t mfr_id; /* Manufacturer ID (IANA Private Enterprise number) */
+    /*
+     * MAC address allocated for an out-of-band management controller, to be
+     * retrieved through NC-SI.
+     */
+    uint8_t oob_eth_addr[6];
 } SlirpConfig;
 
 /* Create a new instance of a slirp stack */
diff --git a/src/slirp.c b/src/slirp.c
index 588cada..54056c9 100644
--- a/src/slirp.c
+++ b/src/slirp.c
@@ -650,8 +650,10 @@ Slirp *slirp_new(const SlirpConfig *cfg, const SlirpCb *callbacks, void *opaque)
 
     if (cfg->version >= 5) {
         slirp->mfr_id = cfg->mfr_id;
+        memcpy(slirp->oob_eth_addr, cfg->oob_eth_addr, ETH_ALEN);
     } else {
         slirp->mfr_id = 0;
+        memset(slirp->oob_eth_addr, 0, ETH_ALEN);
     }
 
     ip6_post_init(slirp);
diff --git a/src/slirp.h b/src/slirp.h
index 4c956d9..e413867 100644
--- a/src/slirp.h
+++ b/src/slirp.h
@@ -152,6 +152,7 @@ struct Slirp {
     bool disable_host_loopback;
 
     uint32_t mfr_id;
+    uint8_t oob_eth_addr[ETH_ALEN];
 
     /* mbuf states */
     struct slirp_quehead m_freelist;