[PATCHv10 3/4] libibverbs: Add API to resolve GID to L2 address

[Eli Cohen <eli-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

Add a new API, resolve_eth_gid(), which resolves a GID to layer 2 address
information. A GID resembles an IPv6 link local address and encodes the MAC
address and the VLAN tag within it. The function accepts the destination GID,
port number and source GID index and returns the MAC, VLAN and indications
whether the remote address is tagged VLAN and whether the address is multicast.

VLAN encoding is done as follows:
gid[11] is MS byte
gid[12] is LS byte

Signed-off-by: Eli Cohen <eli-VPRAkNaXOzVS1MOuV/RT9w@public.gmane.org>
---
Changes from v9:
1. Add missing const in declaration of resolve_eth_gid()
2. Change function name to ibv_resolve_eth_gid()
3. ibv_resolve_eth_gid() requires VLANs retrieved from SGID and DGID be
   indentical only for none multicast GIDs.

 include/infiniband/driver.h |    7 +++
 src/verbs.c                 |   97 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+), 0 deletions(-)

diff --git a/include/infiniband/driver.h b/include/infiniband/driver.h
index 9a81416..dffb26d 100644
--- a/include/infiniband/driver.h
+++ b/include/infiniband/driver.h
@@ -37,6 +37,8 @@
 
 #include <infiniband/verbs.h>
 #include <infiniband/kern-abi.h>
+#include <arpa/inet.h>
+#include <string.h>
 
 #ifdef __cplusplus
 #  define BEGIN_C_DECLS extern "C" {
@@ -143,4 +145,9 @@ const char *ibv_get_sysfs_path(void);
 int ibv_read_sysfs_file(const char *dir, const char *file,
 			char *buf, size_t size);
 
+int ibv_resolve_eth_gid(const struct ibv_pd *pd, uint8_t port_num,
+			union ibv_gid *dgid, uint8_t sgid_index,
+			uint8_t mac[], uint16_t *vlan, uint8_t *tagged,
+			uint8_t *is_mcast);
+
 #endif /* INFINIBAND_DRIVER_H */
diff --git a/src/verbs.c b/src/verbs.c
index ba3c0a4..2cc67c2 100644
--- a/src/verbs.c
+++ b/src/verbs.c
@@ -148,6 +148,7 @@ struct ibv_pd *__ibv_alloc_pd(struct ibv_context *context)
 }
 default_symver(__ibv_alloc_pd, ibv_alloc_pd);
 
+
 int __ibv_dealloc_pd(struct ibv_pd *pd)
 {
 	return pd->context->ops.dealloc_pd(pd);
@@ -543,3 +544,99 @@ int __ibv_detach_mcast(struct ibv_qp *qp, const union ibv_gid *gid, uint16_t lid
 	return qp->context->ops.detach_mcast(qp, gid, lid);
 }
 default_symver(__ibv_detach_mcast, ibv_detach_mcast);
+
+static uint16_t get_vlan_id(const union ibv_gid *dgid)
+{
+	return dgid->raw[11] << 8 | dgid->raw[12];
+}
+
+static void get_ll_mac(const union ibv_gid *gid, uint8_t *mac)
+{
+	memcpy(mac, &gid->raw[8], 3);
+	memcpy(mac + 3, &gid->raw[13], 3);
+	mac[0] ^= 2;
+}
+
+static int is_multicast_gid(const union ibv_gid *gid)
+{
+	return gid->raw[0] == 0xff;
+}
+
+static void get_mcast_mac(const union ibv_gid *gid, uint8_t *mac)
+{
+	int i;
+
+	mac[0] = 0x33;
+	mac[1] = 0x33;
+	for (i = 2; i < 6; ++i)
+		mac[i] = gid->raw[i + 10];
+}
+
+static int is_link_local_gid(const union ibv_gid *gid)
+{
+	uint32_t hi = *(uint32_t *)(gid->raw);
+	uint32_t lo = *(uint32_t *)(gid->raw + 4);
+	if (hi == htonl(0xfe800000) && lo == 0)
+		return 1;
+
+	return 0;
+}
+
+static int resolve_gid(const union ibv_gid *dgid, uint8_t *mac, uint8_t *is_mcast)
+{
+	if (is_link_local_gid(dgid)) {
+		get_ll_mac(dgid, mac);
+		*is_mcast = 0;
+	} else if (is_multicast_gid(dgid)) {
+		get_mcast_mac(dgid, mac);
+		*is_mcast = 1;
+	} else
+		return -EINVAL;
+
+	return 0;
+}
+
+static int is_tagged_vlan(const union ibv_gid *gid)
+{
+	uint16_t tag;
+
+	tag = gid->raw[11] << 8 |  gid->raw[12];
+
+	return tag < 0x1000;
+}
+
+int __ibv_resolve_eth_gid(struct ibv_pd *pd, uint8_t port_num,
+			  const union ibv_gid *dgid, uint8_t sgid_index,
+			  uint8_t mac[], uint16_t *vlan, uint8_t *tagged,
+			  uint8_t *is_mcast)
+{
+	int err;
+	union ibv_gid sgid;
+	int stagged, svlan;
+
+	err = resolve_gid(dgid, mac, is_mcast);
+	if (err)
+		return err;
+
+	err = ibv_query_gid(pd->context, port_num, sgid_index, &sgid);
+	if (err)
+		return err;
+
+	stagged = is_tagged_vlan(&sgid);
+	if (stagged) {
+		if (!is_tagged_vlan(dgid) && !is_mcast)
+			return -1;
+
+		svlan = get_vlan_id(&sgid);
+		if (svlan != get_vlan_id(dgid) && !is_mcast)
+			return -1;
+
+		*tagged = 1;
+		*vlan = svlan;
+	} else
+		*tagged = 0;
+
+	return 0;
+}
+default_symver(__ibv_resolve_eth_gid, ibv_resolve_eth_gid);
+
-- 
1.7.2.2

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