[netdevice] Split multicast hashing out into an mc_hash method

Multicast hashing is an ugly overlap between network and link layers.
EFI requires us to provide access to this functionality, so move it
out of ipv4.c and expose it as a method of the link layer.

1 files changed, 30 insertions, 2 deletions

diff --git a/src/net/ethernet.c b/src/net/ethernet.c
index 7b1c496f..ebb551f0 100644
--- a/src/net/ethernet.c
+++ b/src/net/ethernet.c
@@ -24,6 +24,7 @@
 #include <assert.h>
 #include <gpxe/if_arp.h>
 #include <gpxe/if_ether.h>
+#include <gpxe/in.h>
 #include <gpxe/netdevice.h>
 #include <gpxe/iobuf.h>
 #include <gpxe/ethernet.h>
@@ -92,8 +93,8 @@ static int eth_pull ( struct io_buffer *iobuf,
 /**
  * Transcribe Ethernet address
  *
- * @v ll_addr	Link-layer address
- * @ret string	Link-layer address in human-readable format
+ * @v ll_addr		Link-layer address
+ * @ret string		Link-layer address in human-readable format
  */
 const char * eth_ntoa ( const void *ll_addr ) {
 	static char buf[18]; /* "00:00:00:00:00:00" */
@@ -105,6 +106,32 @@ const char * eth_ntoa ( const void *ll_addr ) {
 	return buf;
 }
 
+/**
+ * Hash multicast address
+ *
+ * @v af		Address family
+ * @v net_addr		Network-layer address
+ * @v ll_addr		Link-layer address to fill in
+ * @ret rc		Return status code
+ */
+static int eth_mc_hash ( unsigned int af, const void *net_addr,
+			 void *ll_addr ) {
+	const uint8_t *net_addr_bytes = net_addr;
+	uint8_t *ll_addr_bytes = ll_addr;
+
+	switch ( af ) {
+	case AF_INET:
+		ll_addr_bytes[0] = 0x01;
+		ll_addr_bytes[1] = 0x00;
+		ll_addr_bytes[2] = 0x5e;
+		ll_addr_bytes[3] = net_addr_bytes[1] & 0x7f;
+		ll_addr_bytes[4] = net_addr_bytes[2];
+		ll_addr_bytes[5] = net_addr_bytes[3];
+	default:
+		return -ENOTSUP;
+	}
+}
+
 /** Ethernet protocol */
 struct ll_protocol ethernet_protocol __ll_protocol = {
 	.name		= "Ethernet",
@@ -115,4 +142,5 @@ struct ll_protocol ethernet_protocol __ll_protocol = {
 	.push		= eth_push,
 	.pull		= eth_pull,
 	.ntoa		= eth_ntoa,
+	.mc_hash	= eth_mc_hash,
 };