libopeniscsiusr: Add basic iface support into iscsi session.

 * New function `iscsi_session_iface_get()` to query in use iface of
   specified iscsi session.

 * Only basic information included required by command
   'iscsiadm -m session -P 3'

 * The iface name does not support old kernel yet. Will fix that in
   full iface support patches.

Signed-off-by: Gris Ge <fge@redhat.com>

11 files changed, 670 insertions, 2 deletions

diff --git a/libopeniscsiusr/Makefile b/libopeniscsiusr/Makefile
index 143a177..8b9b523 100644
--- a/libopeniscsiusr/Makefile
+++ b/libopeniscsiusr/Makefile
@@ -34,11 +34,12 @@ LIBS_MAJOR = $(DEVLIB).$(LIBISCSI_USR_VERSION_MAJOR)
 PKGFILE = libopeniscsiusr.pc
 HEADERS = libopeniscsiusr/libopeniscsiusr.h \
 	  libopeniscsiusr/libopeniscsiusr_common.h \
-	  libopeniscsiusr/libopeniscsiusr_session.h
+	  libopeniscsiusr/libopeniscsiusr_session.h \
+	  libopeniscsiusr/libopeniscsiusr_iface.h
 TESTS = tests/test_context tests/test_session
 EXTRA_MAN_FILES = libopeniscsiusr.h.3
 
-OBJS = context.o misc.o session.o sysfs.o
+OBJS = context.o misc.o session.o sysfs.o iface.o
 
 CFLAGS ?= -O2 -g
 CFLAGS += -Wall -Werror -Wextra -fvisibility=hidden -fPIC
diff --git a/libopeniscsiusr/iface.c b/libopeniscsiusr/iface.c
new file mode 100644
index 0000000..79898df
--- /dev/null
+++ b/libopeniscsiusr/iface.c
@@ -0,0 +1,289 @@
+/*
+ * Copyright (C) 2017 Red Hat, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Gris Ge <fge@redhat.com>
+ */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE			/* For NI_MAXHOST */
+#endif
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <dirent.h>
+#include <string.h>
+#include <net/if.h>
+#include <netdb.h>
+#include <assert.h>
+#include <inttypes.h>
+
+#include "libopeniscsiusr/libopeniscsiusr.h"
+#include "misc.h"
+#include "sysfs.h"
+#include "iface.h"
+
+#define ISCSI_MAX_IFACE_LEN			65
+#define ISCSI_TRANSPORT_NAME_MAXLEN		16
+#define ISCSI_MAX_STR_LEN			80
+#define ISCSI_HWADDRESS_BUF_SIZE		18
+#define TARGET_NAME_MAXLEN			255
+/* ^ TODO(Gris Ge): Above 5 constants are copy from usr/config.h, need to
+ *		    verify them in linux kernel code
+ */
+
+#define DEFAULT_IFACENAME	"default"
+#define DEFAULT_NETDEV		"default"
+#define DEFAULT_IPADDRESS	"default"
+#define DEFAULT_HWADDRESS	"default"
+
+
+/* Just copy from `struct iface_rec` from usr/config.h */
+struct iscsi_iface {
+	/* iscsi iface record name */
+	char			name[ISCSI_MAX_IFACE_LEN];
+	uint32_t		iface_num;
+	/* network layer iface name (eth0) */
+	char			netdev[IFNAMSIZ];
+	char			ipaddress[NI_MAXHOST];
+	char			subnet_mask[NI_MAXHOST];
+	char			gateway[NI_MAXHOST];
+	char			bootproto[ISCSI_MAX_STR_LEN];
+	char			ipv6_linklocal[NI_MAXHOST];
+	char			ipv6_router[NI_MAXHOST];
+	char			ipv6_autocfg[NI_MAXHOST];
+	char			linklocal_autocfg[NI_MAXHOST];
+	char			router_autocfg[NI_MAXHOST];
+	uint16_t		vlan_id;
+	uint8_t			vlan_priority;
+	char			vlan_state[ISCSI_MAX_STR_LEN];
+	char			state[ISCSI_MAX_STR_LEN]; /* 0 = disable,
+							   * 1 = enable */
+	uint16_t		mtu;
+	uint16_t		port;
+	char			delayed_ack[ISCSI_MAX_STR_LEN];
+	char			nagle[ISCSI_MAX_STR_LEN];
+	char			tcp_wsf_state[ISCSI_MAX_STR_LEN];
+	uint8_t			tcp_wsf;
+	uint8_t			tcp_timer_scale;
+	char			tcp_timestamp[ISCSI_MAX_STR_LEN];
+	char			dhcp_dns[ISCSI_MAX_STR_LEN];
+	char			dhcp_slp_da[ISCSI_MAX_STR_LEN];
+	char			tos_state[ISCSI_MAX_STR_LEN];
+	uint8_t			tos;
+	char			gratuitous_arp[ISCSI_MAX_STR_LEN];
+	char			dhcp_alt_client_id_state[ISCSI_MAX_STR_LEN];
+	char			dhcp_alt_client_id[ISCSI_MAX_STR_LEN];
+	char			dhcp_req_vendor_id_state[ISCSI_MAX_STR_LEN];
+	char			dhcp_vendor_id_state[ISCSI_MAX_STR_LEN];
+	char			dhcp_vendor_id[ISCSI_MAX_STR_LEN];
+	char			dhcp_learn_iqn[ISCSI_MAX_STR_LEN];
+	char			fragmentation[ISCSI_MAX_STR_LEN];
+	char			incoming_forwarding[ISCSI_MAX_STR_LEN];
+	uint8_t			ttl;
+	char			gratuitous_neighbor_adv[ISCSI_MAX_STR_LEN];
+	char			redirect[ISCSI_MAX_STR_LEN];
+	char			mld[ISCSI_MAX_STR_LEN];
+	uint32_t		flow_label;
+	uint32_t		traffic_class;
+	uint8_t			hop_limit;
+	uint32_t		nd_reachable_tmo;
+	uint32_t		nd_rexmit_time;
+	uint32_t		nd_stale_tmo;
+	uint8_t			dup_addr_detect_cnt;
+	uint32_t		router_adv_link_mtu;
+	uint16_t		def_task_mgmt_tmo;
+	char			header_digest[ISCSI_MAX_STR_LEN];
+	char			data_digest[ISCSI_MAX_STR_LEN];
+	char			immediate_data[ISCSI_MAX_STR_LEN];
+	char			initial_r2t[ISCSI_MAX_STR_LEN];
+	char			data_seq_inorder[ISCSI_MAX_STR_LEN];
+	char			data_pdu_inorder[ISCSI_MAX_STR_LEN];
+	uint8_t			erl;
+	uint32_t		max_recv_dlength;
+	uint32_t		first_burst_len;
+	uint16_t		max_out_r2t;
+	uint32_t		max_burst_len;
+	char			chap_auth[ISCSI_MAX_STR_LEN];
+	char			bidi_chap[ISCSI_MAX_STR_LEN];
+	char			strict_login_comp[ISCSI_MAX_STR_LEN];
+	char			discovery_auth[ISCSI_MAX_STR_LEN];
+	char			discovery_logout[ISCSI_MAX_STR_LEN];
+	char			port_state[ISCSI_MAX_STR_LEN];
+	char			port_speed[ISCSI_MAX_STR_LEN];
+	/*
+	 * TODO: we may have to make this bigger and interconnect
+	 * specific for infiniband
+	 */
+	char			hwaddress[ISCSI_HWADDRESS_BUF_SIZE];
+	char			transport_name[ISCSI_TRANSPORT_NAME_MAXLEN];
+	/*
+	 * This is only used for boot now, but the iser guys
+	 * can use this for their virtualization idea.
+	 */
+	char			alias[TARGET_NAME_MAXLEN + 1];
+	char			iname[TARGET_NAME_MAXLEN + 1];
+};
+
+_iscsi_getter_func_gen(iscsi_iface, hwaddress, const char *);
+_iscsi_getter_func_gen(iscsi_iface, transport_name, const char *);
+_iscsi_getter_func_gen(iscsi_iface, ipaddress, const char *);
+_iscsi_getter_func_gen(iscsi_iface, netdev, const char *);
+_iscsi_getter_func_gen(iscsi_iface, iname, const char *);
+_iscsi_getter_func_gen(iscsi_iface, port_state, const char *);
+_iscsi_getter_func_gen(iscsi_iface, port_speed, const char *);
+_iscsi_getter_func_gen(iscsi_iface, name, const char *);
+
+int _iscsi_iface_get(struct iscsi_context *ctx, uint32_t host_id, uint32_t sid,
+		     const char *iface_kern_id, struct iscsi_iface **iface)
+{
+	int rc = LIBISCSI_OK;
+	char sysfs_se_dir_path[PATH_MAX];
+	char sysfs_sh_dir_path[PATH_MAX];
+	char sysfs_scsi_host_dir_path[PATH_MAX];
+	char sysfs_iface_dir_path[PATH_MAX];
+	char proc_name[ISCSI_TRANSPORT_NAME_MAXLEN];
+
+	assert(ctx != NULL);
+	assert(host_id != 0);
+	assert(sid != 0);
+	/* TODO(Gris Ge): Handle when sid == 0(ignored) */
+	assert(iface != NULL);
+
+	*iface = NULL;
+
+	*iface = (struct iscsi_iface *) malloc(sizeof(struct iscsi_iface));
+	_alloc_null_check(ctx, *iface, rc, out);
+
+	snprintf(sysfs_se_dir_path, PATH_MAX, "%s/session%" PRIu32,
+		 _ISCSI_SYS_SESSION_DIR, sid);
+	snprintf(sysfs_sh_dir_path, PATH_MAX, "%s/host%" PRIu32,
+		 _ISCSI_SYS_HOST_DIR, host_id);
+	snprintf(sysfs_scsi_host_dir_path, PATH_MAX, "%s/host%" PRIu32,
+		 _SCSI_SYS_HOST_DIR, host_id);
+	if (iface_kern_id != NULL)
+		snprintf(sysfs_iface_dir_path, PATH_MAX, "%s/%s",
+			 _ISCSI_SYS_IFACE_DIR, iface_kern_id);
+
+	_good(_sysfs_prop_get_str(ctx, sysfs_scsi_host_dir_path, "proc_name",
+				  proc_name, sizeof(proc_name) / sizeof(char),
+				  NULL /* raise error if failed */),
+	      rc, out);
+
+	if (strncmp(proc_name, "iscsi_", strlen("iscsi_")) == 0)
+		strncpy((*iface)->transport_name, proc_name + strlen("iscsi_"),
+			sizeof((*iface)->transport_name) / sizeof(char));
+	else
+		strncpy((*iface)->transport_name, proc_name,
+			sizeof((*iface)->transport_name) / sizeof(char));
+
+	_good(_sysfs_prop_get_str(ctx, sysfs_sh_dir_path, "hwaddress",
+				  (*iface)->hwaddress,
+				  sizeof((*iface)->hwaddress) / sizeof(char),
+				  DEFAULT_HWADDRESS),
+	      rc, out);
+
+	if (iface_kern_id != NULL)
+		_good(_sysfs_prop_get_str(ctx, sysfs_iface_dir_path,
+					  "ipaddress",
+					  (*iface)->ipaddress,
+					  sizeof((*iface)->ipaddress) /
+					  sizeof(char), DEFAULT_IPADDRESS),
+		      rc, out);
+	else
+		_good(_sysfs_prop_get_str(ctx, sysfs_sh_dir_path, "ipaddress",
+					(*iface)->ipaddress,
+					sizeof((*iface)->ipaddress) /
+					sizeof(char), DEFAULT_IPADDRESS),
+		      rc, out);
+
+	_good(_sysfs_prop_get_str(ctx, sysfs_sh_dir_path, "netdev",
+				  (*iface)->netdev,
+				  sizeof((*iface)->netdev) / sizeof(char),
+				  DEFAULT_NETDEV),
+	      rc, out);
+
+	if (_sysfs_prop_get_str(NULL /* Ignore error */, sysfs_se_dir_path,
+				  "initiatorname",
+				  (*iface)->iname,
+				  sizeof((*iface)->iname) / sizeof(char),
+				  "")
+	    != LIBISCSI_OK) {
+		_debug(ctx, "Failed to read initiatorname from %s folder",
+		       sysfs_se_dir_path);
+		_good(_sysfs_prop_get_str(ctx, sysfs_sh_dir_path,
+					  "initiatorname", (*iface)->iname,
+					  sizeof((*iface)->iname) /
+					  sizeof(char), ""),
+		      rc, out);
+	}
+
+	_good(_sysfs_prop_get_str(ctx, sysfs_sh_dir_path, "port_state",
+				  (*iface)->port_state,
+				  sizeof((*iface)->port_state) / sizeof(char),
+				  "unknown"),
+	      rc, out);
+
+	if (strcmp((*iface)->port_state, "Unknown!") == 0)
+		strncpy((*iface)->port_state, "unknown",
+			sizeof((*iface)->port_state) / sizeof(char));
+
+	_good(_sysfs_prop_get_str(ctx, sysfs_sh_dir_path, "port_speed",
+				  (*iface)->port_speed,
+				  sizeof((*iface)->port_speed) / sizeof(char),
+				  "unknown"),
+	      rc, out);
+
+	if (strncmp((*iface)->port_speed, "Unknown", strlen("Unknown")) == 0)
+		strncpy((*iface)->port_speed, "unknown",
+			sizeof((*iface)->port_speed) / sizeof(char));
+
+	_good(_sysfs_prop_get_str(NULL /* Ignore error */, sysfs_se_dir_path,
+				  "ifacename",
+				  (*iface)->name,
+				  sizeof((*iface)->name)/sizeof(char),
+				  ""),
+	      rc, out);
+	if (strcmp((*iface)->name, "") == 0) {
+		_debug(ctx, "Failed to query ifacename from %s folder",
+		       sysfs_se_dir_path);
+		/*
+		 * if the ifacename file is not there then we are
+		 * using a older kernel and can try to find the
+		 * binding by the net info which was used on these
+		 * older kernels.
+		 */
+
+		/*TODO(Gris Ge): need to parse /etc/iscsi/ifaces/<iface_name>
+		 * files to find a match. I will add the code later when
+		 * we expose more defiled information on iscsi_iface.
+		 */
+		strncpy((*iface)->name, DEFAULT_IFACENAME,
+			sizeof((*iface)->name) / sizeof(char));
+	}
+
+out:
+	if (rc != LIBISCSI_OK) {
+		_iscsi_iface_free(*iface);
+		*iface = NULL;
+	}
+	return rc;
+}
+
+void _iscsi_iface_free(struct iscsi_iface *iface)
+{
+	free(iface);
+}
diff --git a/libopeniscsiusr/iface.h b/libopeniscsiusr/iface.h
new file mode 100644
index 0000000..85aa97c
--- /dev/null
+++ b/libopeniscsiusr/iface.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2017 Red Hat, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Gris Ge <fge@redhat.com>
+ */
+#ifndef __ISCSI_USR_IFACE_H__
+#define __ISCSI_USR_IFACE_H__
+
+#include "libopeniscsiusr/libopeniscsiusr_common.h"
+#include <stdint.h>
+
+/*
+ * BUG(Gris Ge): Should include 'iface_kern_id' parameter.
+ */
+__DLL_LOCAL int _iscsi_iface_get(struct iscsi_context *ctx, uint32_t host_id,
+				 uint32_t sid, const char *iface_kern_id,
+				 struct iscsi_iface **iface);
+
+__DLL_LOCAL void _iscsi_iface_free(struct iscsi_iface *iface);
+
+
+#endif /* End of __ISCSI_USR_IFACE_H__ */
diff --git a/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr.h b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr.h
index 45d42c1..bf8a845 100644
--- a/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr.h
+++ b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr.h
@@ -28,6 +28,7 @@ extern "C" {
 
 #include "libopeniscsiusr_common.h"
 #include "libopeniscsiusr_session.h"
+#include "libopeniscsiusr_iface.h"
 
 /**
  * iscsi_log_priority_str() - Convert log priority to string.
diff --git a/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_common.h b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_common.h
index b001904..383ff19 100644
--- a/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_common.h
+++ b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_common.h
@@ -65,4 +65,6 @@ struct __DLL_EXPORT iscsi_context;
 
 struct __DLL_EXPORT iscsi_session;
 
+struct __DLL_EXPORT iscsi_iface;
+
 #endif /* End of _LIB_OPEN_ISCSI_USR_COMMON_H_ */
diff --git a/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_iface.h b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_iface.h
new file mode 100644
index 0000000..ffba1f7
--- /dev/null
+++ b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_iface.h
@@ -0,0 +1,176 @@
+/*
+ * Copyright (C) 2017 Red Hat, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Gris Ge <fge@redhat.com>
+ */
+
+#ifndef _LIB_OPEN_ISCSI_USR_IFACE_H_
+#define _LIB_OPEN_ISCSI_USR_IFACE_H_
+
+#include "libopeniscsiusr_common.h"
+
+/**
+ * iscsi_iface_ipaddress_get() - Retrieve IP address of specified
+ * iSCSI interface
+ *
+ * Retrieve the IP address of specified iSCSI interface.
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_ipaddress_get(struct iscsi_iface *iface);
+
+/**
+ * iscsi_iface_hwaddress_get() - Retrieve hardware address of specified
+ * iSCSI interface
+ *
+ * Retrieve the hardware address of specified iSCSI interface.
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_hwaddress_get(struct iscsi_iface *iface);
+
+/**
+ * iscsi_iface_netdev_get() - Retrieve network device name of specified
+ * iSCSI interface
+ *
+ * Retrieve the network device name of specified iSCSI interface.
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_netdev_get(struct iscsi_iface *iface);
+
+/**
+ * iscsi_iface_transport_name_get() - Retrieve transport name of specified
+ * iSCSI interface
+ *
+ * Retrieve the transport name of specified iSCSI interface.
+ * Examples:
+ *
+ *	* "tcp" (Software iSCSI over TCP/IP)
+ *	* "iser" (Software iSCSI over infinniband
+ *	* "qla4xxx" (Qlogic QLA4XXX HBAs)
+ *	* "bnx2i" (Broadcom bnx iSCSI HBAs);
+ *	* "cxgb3i" (Chelsio cxgb S3 iSCSI HBAs);
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_transport_name_get
+	(struct iscsi_iface *iface);
+
+/**
+ * iscsi_iface_iname_get() - Retrieve initiator name of specified
+ * iSCSI interface
+ *
+ * Retrieve the initiator name of specified iSCSI interface.
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_iname_get(struct iscsi_iface *iface);
+
+/**
+ * iscsi_iface_port_state_get() - Retrieve network port state of specified
+ * iSCSI interface
+ *
+ * Retrieve the network port state of specified iSCSI interface.
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *. Possible values are :
+ *
+ *	* "LINK_UP"
+ *
+ *	* "LINK_DOWN"
+ *
+ *	* "unknown"
+ *
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_port_state_get(struct iscsi_iface *iface);
+
+/**
+ * iscsi_iface_port_speed_get() - Retrieve network port speed of specified
+ * iSCSI interface
+ *
+ * Retrieve the network port speed of specified iSCSI interface.
+ * Returned string format is '[0-9]+ [MGT]bps', example: '10 Mbps' or '10 Gbps'.
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *. Set to "unknown" if unknown.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_port_speed_get(struct iscsi_iface *iface);
+
+/**
+ * iscsi_iface_port_speed_get() - Retrieve name of specified iSCSI interface
+ *
+ * Retrieve the name of specified iSCSI interface.
+ *
+ * @iface:
+ *	Pointer of 'struct iscsi_iface'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	const char *.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT const char *iscsi_iface_name_get(struct iscsi_iface *iface);
+
+#endif /* End of _LIB_OPEN_ISCSI_USR_IFACE_H_ */
diff --git a/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_session.h b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_session.h
index 4397258..30f8d7a 100644
--- a/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_session.h
+++ b/libopeniscsiusr/libopeniscsiusr/libopeniscsiusr_session.h
@@ -328,4 +328,24 @@ __DLL_EXPORT const char *iscsi_session_address_get
  */
 __DLL_EXPORT int32_t iscsi_session_port_get(struct iscsi_session *se);
 
+/**
+ * iscsi_session_address_get() - Retrieve iSCSI interface information of
+ * specified session
+ *
+ * Retrieve the iSCSI interface information of specified iSCSI session.
+ * For the properties of 'struct iscsi_iface', please refer to the functions
+ * defined in 'libopeniscsiusr_iface.h' file.
+ *
+ * @se:
+ *	Pointer of 'struct iscsi_session'.
+ *	If this pointer is NULL, your program will be terminated by assert.
+ *
+ * Return:
+ *	Pointer of 'struct iscsi_iface'. NULL if not supported.
+ *	No need to free this memory, the resources will get freed by
+ *	iscsi_session_free() or iscsi_sessions_free().
+ */
+__DLL_EXPORT struct iscsi_iface *iscsi_session_iface_get
+	(struct iscsi_session *se);
+
 #endif /* End of _LIB_OPEN_ISCSI_USR_SESSION_H_ */
diff --git a/libopeniscsiusr/session.c b/libopeniscsiusr/session.c
index b7b39b2..ea3d9bc 100644
--- a/libopeniscsiusr/session.c
+++ b/libopeniscsiusr/session.c
@@ -35,6 +35,7 @@
 #include "libopeniscsiusr/libopeniscsiusr.h"
 #include "misc.h"
 #include "sysfs.h"
+#include "iface.h"
 
 #define _ISCSI_NAME_MAX_LEN		223
 /* ^ RFC 3720:
@@ -80,6 +81,7 @@ struct iscsi_session {
 	char address[NI_MAXHOST + 1];
 
 	int32_t port;
+	struct iscsi_iface *iface;
 };
 
 static uint32_t session_str_to_sid(const char *session_str);
@@ -99,6 +101,7 @@ _iscsi_getter_func_gen(iscsi_session, abort_tmo, int32_t);
 _iscsi_getter_func_gen(iscsi_session, tpgt, int32_t);
 _iscsi_getter_func_gen(iscsi_session, address, const char *);
 _iscsi_getter_func_gen(iscsi_session, port, int32_t);
+_iscsi_getter_func_gen(iscsi_session, iface, struct iscsi_iface *);
 
 /*
  * The session string is "session%u" used by /sys/class/iscsi_session/session%u.
@@ -119,6 +122,7 @@ int iscsi_session_get(struct iscsi_context *ctx, uint32_t sid,
 	int rc = LIBISCSI_OK;
 	char sysfs_se_dir_path[PATH_MAX];
 	char sysfs_con_dir_path[PATH_MAX];
+	uint32_t host_id = 0;
 
 	assert(ctx != NULL);
 	assert(se != NULL);
@@ -243,6 +247,12 @@ int iscsi_session_get(struct iscsi_context *ctx, uint32_t sid,
 	    ((*se)->port == -1))
 		(*se)->port = (*se)->persistent_port;
 
+	_good(_iscsi_host_id_of_session(ctx, sid, &host_id), rc, out);
+
+	_good(_iscsi_iface_get(ctx, host_id, sid, NULL /*iface kernel id */,
+			       &((*se)->iface)),
+	      rc, out);
+
 out:
 	if (rc != LIBISCSI_OK) {
 		iscsi_session_free(*se);
@@ -323,6 +333,8 @@ out:
 
 void iscsi_session_free(struct iscsi_session *se)
 {
+	if (se != NULL)
+		_iscsi_iface_free(se->iface);
 	free(se);
 }
 
diff --git a/libopeniscsiusr/sysfs.c b/libopeniscsiusr/sysfs.c
index c1aa576..70298f2 100644
--- a/libopeniscsiusr/sysfs.c
+++ b/libopeniscsiusr/sysfs.c
@@ -48,6 +48,9 @@ static int iscsi_sysfs_prop_get_ll(struct iscsi_context *ctx,
 				   const char *dir_path, const char *prop_name,
 				   long long int *val,
 				   long long int default_value);
+static int sysfs_get_dev_path(struct iscsi_context *ctx, const char *path,
+			      char *dev_path);
+
 /*
  * dev_path should be char[PATH_MAX].
  */
@@ -240,3 +243,109 @@ int _sysfs_prop_get_i32(struct iscsi_context *ctx, const char *dir_path,
 		*val = tmp_val & INT32_MAX;
 	return rc;
 }
+
+static int sysfs_get_dev_path(struct iscsi_context *ctx, const char *path,
+			      char *dev_path)
+{
+	int rc = LIBISCSI_OK;
+	int errno_save = 0;
+	regex_t regex;
+	regmatch_t reg_match[2];
+	int reg_rc = 0;
+	int need_free_reg = 0;
+
+	assert(ctx != NULL);
+	assert(path != NULL);
+	assert(dev_path != NULL);
+
+	memset(dev_path, 0, PATH_MAX);
+
+	if (realpath(path, dev_path) == NULL) {
+		errno_save = errno;
+		rc = LIBISCSI_ERR_SYSFS_LOOKUP;
+		_error(ctx, "realpath() failed on %s with error %d", path,
+		       errno_save);
+		goto out;
+	}
+
+	reg_rc = regcomp(&regex,
+			 "\\(.\\{1,\\}/devices/.\\{1,\\}/host[0-9]\\{1,\\}\\)/"
+			 "session[0-9]\\{1,\\}/iscsi_session/",
+			 0 /* no flag */);
+	/* ^ BUG(Gris Ge): This is based on GUESS, should check linux kernel
+	 *		   code on this
+	 */
+	if (reg_rc != 0) {
+		rc = LIBISCSI_ERR_SYSFS_LOOKUP;
+		_error(ctx, "regcomp() failed %d", reg_rc);
+		goto out;
+	}
+	need_free_reg = 1;
+	if (regexec(&regex, dev_path, 2 /* count of max matches */,
+		    reg_match, 0 /* no flags */) != 0) {
+		rc = LIBISCSI_ERR_SYSFS_LOOKUP;
+		_error(ctx, "regexec() not match for %s", dev_path);
+		goto out;
+	}
+
+	*(dev_path + reg_match[1].rm_eo ) = '\0';
+
+	_debug(ctx, "Got dev path of '%s': '%s'", path, dev_path);
+
+out:
+	if (need_free_reg)
+		regfree(&regex);
+	if (rc != LIBISCSI_OK)
+		memset(dev_path, 0, PATH_MAX);
+	return rc;
+}
+
+int _iscsi_host_id_of_session(struct iscsi_context *ctx, uint32_t sid,
+			      uint32_t *host_id)
+{
+	int rc = LIBISCSI_OK;
+	char sys_se_dir_path[PATH_MAX];
+	char sys_dev_path[PATH_MAX];
+	char sys_scsi_host_dir_path[PATH_MAX];
+	struct dirent **namelist = NULL;
+	int n = 0;
+	const char *host_id_str = NULL;
+	int i = 0;
+
+	assert(ctx != NULL);
+	assert(sid != 0);
+	assert(host_id != NULL);
+
+	snprintf(sys_se_dir_path, PATH_MAX, "%s/session%" PRIu32,
+		 _ISCSI_SYS_SESSION_DIR, sid);
+
+	*host_id = 0;
+
+	_good(sysfs_get_dev_path(ctx, sys_se_dir_path, sys_dev_path), rc, out);
+
+	snprintf(sys_scsi_host_dir_path, PATH_MAX, "%s/iscsi_host/",
+		 sys_dev_path);
+
+	n = scandir(sys_scsi_host_dir_path, &namelist, _scan_filter_skip_dot,
+		    alphasort);
+	if (n != 1) {
+		rc = LIBISCSI_ERR_SYSFS_LOOKUP;
+		_error(ctx, "Got unexpected(should be 1) file in folder %s",
+		       sys_scsi_host_dir_path);
+		goto out;
+	}
+	host_id_str = namelist[0]->d_name;
+
+	if (sscanf(host_id_str, "host%" SCNu32, host_id) != 1) {
+		rc = LIBISCSI_ERR_SYSFS_LOOKUP;
+		_error(ctx, "sscanf() failed on string %s", host_id_str);
+		goto out;
+	}
+
+out:
+	for (i = n - 1; i >= 0; --i)
+		free(namelist[i]);
+	free(namelist);
+
+	return rc;
+}
diff --git a/libopeniscsiusr/sysfs.h b/libopeniscsiusr/sysfs.h
index 835c0fe..3b501c2 100644
--- a/libopeniscsiusr/sysfs.h
+++ b/libopeniscsiusr/sysfs.h
@@ -25,6 +25,9 @@
 
 #define _ISCSI_SYS_SESSION_DIR		"/sys/class/iscsi_session"
 #define _ISCSI_SYS_CONNECTION_DIR	"/sys/class/iscsi_connection"
+#define _ISCSI_SYS_HOST_DIR		"/sys/class/iscsi_host"
+#define _ISCSI_SYS_IFACE_DIR		"/sys/class/iscsi_iface"
+#define _SCSI_SYS_HOST_DIR		"/sys/class/scsi_host"
 
 /*
  * When default_value == NULL, treat no such file as LIB_BUG.
@@ -48,4 +51,7 @@ __DLL_LOCAL int _sysfs_prop_get_i32(struct iscsi_context *ctx,
 				    const char *dir_path, const char *prop_name,
 				    int32_t *val, int32_t default_value);
 
+__DLL_LOCAL int _iscsi_host_id_of_session(struct iscsi_context *ctx,
+					  uint32_t sid, uint32_t *host_id);
+
 #endif /* End of __ISCSI_USR_SYSFS_H__ */
diff --git a/libopeniscsiusr/tests/test_session.c b/libopeniscsiusr/tests/test_session.c
index f7abc03..0f23f2e 100644
--- a/libopeniscsiusr/tests/test_session.c
+++ b/libopeniscsiusr/tests/test_session.c
@@ -58,6 +58,22 @@
 	} while(0)
 
 static void test_session(struct iscsi_session *se);
+static void test_iface(struct iscsi_iface *iface);
+
+static void test_iface(struct iscsi_iface *iface)
+{
+	assert(iface != NULL);
+	printf("\t#### Interface info ####\n");
+	_assert_print_prop_str_not_empty(iscsi_iface, iface, name);
+	_assert_print_prop_str_not_empty(iscsi_iface, iface, ipaddress);
+	_assert_print_prop_str_not_empty(iscsi_iface, iface, transport_name);
+	_assert_print_prop_str_not_empty(iscsi_iface, iface, iname);
+	_assert_print_prop_str_can_empty(iscsi_iface, iface, hwaddress);
+	_assert_print_prop_str_can_empty(iscsi_iface, iface, netdev);
+	_assert_print_prop_str_can_empty(iscsi_iface, iface, port_state);
+	_assert_print_prop_str_can_empty(iscsi_iface, iface, port_speed);
+	printf("\t########################\n");
+}
 
 static void test_session(struct iscsi_session *se)
 {
@@ -99,6 +115,7 @@ int main()
 		printf("\nGot %" PRIu32 " iSCSI sessions\n", se_count);
 		for (i = 0; i < se_count; ++i) {
 			test_session(ses[i]);
+			test_iface(iscsi_session_iface_get(ses[i]));
 		}
 		iscsi_sessions_free(ses, se_count);
 	}