git: 72467b39f1db - stable/13 - netlink: return optional metadata with the operation result.

From: Alexander V. Chernikov <melifaro_at_FreeBSD.org>
Date: Mon, 20 Feb 2023 14:34:05 UTC
The branch stable/13 has been updated by melifaro:

URL: https://cgit.FreeBSD.org/src/commit/?id=72467b39f1db794f2ac54ac9baa1de3166507c6b

commit 72467b39f1db794f2ac54ac9baa1de3166507c6b
Author:     Alexander V. Chernikov <melifaro@FreeBSD.org>
AuthorDate: 2023-02-09 14:53:44 +0000
Commit:     Alexander V. Chernikov <melifaro@FreeBSD.org>
CommitDate: 2023-02-20 14:33:28 +0000

    netlink: return optional metadata with the operation result.
    
    Some operations like interface creation may need to return metadata
     - in this case, interface name - back to the caller if the operation
     is successful.
    This change implements attaching an `NLMSGERR_ATTR_COOKIE` nla to the
    operation reply message via `nlmsg_report_cookie()`.
    Additionally, on successful interface creation, interface index and
     interface name are returned in the `IFLA_NEW_IFINDEX` and `IFLA_IFNAME
     TLVs, encapsulated in the `NLMSGERR_ATTR_COOKIE`.
    
    Reviewed By: pauamma
    Differential Revision: https://reviews.freebsd.org/D38283
    MFC after:      1 week
    
    (cherry picked from commit 25c2dd2f2c6c6144d59d463c95f0471301d6efaa)
---
 share/man/man4/netlink.4             |   4 ++
 share/man/man4/rtnetlink.4           |   7 ++
 sys/netlink/netlink_message_parser.c |  19 +++++
 sys/netlink/netlink_message_parser.h |   4 ++
 sys/netlink/netlink_message_writer.c |   6 +-
 sys/netlink/netlink_message_writer.h |  31 ++++++++
 sys/netlink/route/iface_drivers.c    |  37 ++++++++++
 tests/atf_python/sys/net/netlink.py  | 134 +++++++++++++++++++----------------
 tests/sys/netlink/test_rtnl_iface.py |  35 +++++++++
 9 files changed, 213 insertions(+), 64 deletions(-)

diff --git a/share/man/man4/netlink.4 b/share/man/man4/netlink.4
index 1894de5841fe..fdcc823b01a6 100644
--- a/share/man/man4/netlink.4
+++ b/share/man/man4/netlink.4
@@ -217,6 +217,10 @@ socket option is set, the kernel may add a
 string TLV with the textual error description, optionally followed by the
 .Dv NLMSGERR_ATTR_OFFS
 TLV, indicating the offset from the message start that triggered an error.
+Some operations may return additional metadata encapsulated in the
+.Dv NLMSGERR_ATTR_COOKIE
+TLV.
+The metadata format is specific to the operation.
 If the operation reply is a multipart message, then no
 .Dv NLMSG_ERROR
 reply is generated, only a
diff --git a/share/man/man4/rtnetlink.4 b/share/man/man4/rtnetlink.4
index 5849508b74c2..2c601251f7b0 100644
--- a/share/man/man4/rtnetlink.4
+++ b/share/man/man4/rtnetlink.4
@@ -284,6 +284,13 @@ struct ifinfomsg {
 Creates a new interface.
 The only mandatory TLV is
 .Dv IFLA_IFNAME .
+The following attributes are returned inside the nested
+.Dv NLMSGERR_ATTR_COOKIE :
+.Pp
+.Bd -literal -offset indent -compact
+IFLA_NEW_IFINDEX	(uint32) created interface index
+IFLA_IFNAME		(string) created interface name
+.Ed
 .Ss RTM_DELLINK
 Deletes the interface specified by
 .Dv IFLA_IFNAME .
diff --git a/sys/netlink/netlink_message_parser.c b/sys/netlink/netlink_message_parser.c
index dc0c38712613..e30138266d9d 100644
--- a/sys/netlink/netlink_message_parser.c
+++ b/sys/netlink/netlink_message_parser.c
@@ -78,6 +78,25 @@ nlmsg_report_err_offset(struct nl_pstate *npt, uint32_t off)
 	return (true);
 }
 
+void
+nlmsg_report_cookie(struct nl_pstate *npt, struct nlattr *nla)
+{
+	MPASS(nla->nla_type == NLMSGERR_ATTR_COOKIE);
+	MPASS(nla->nla_len >= sizeof(struct nlattr));
+	npt->cookie = nla;
+}
+
+void
+nlmsg_report_cookie_u32(struct nl_pstate *npt, uint32_t val)
+{
+	struct nlattr *nla = npt_alloc(npt, sizeof(*nla) + sizeof(uint32_t));
+
+	nla->nla_type = NLMSGERR_ATTR_COOKIE;
+	nla->nla_len = sizeof(*nla) + sizeof(uint32_t);
+	memcpy(nla + 1, &val, sizeof(uint32_t));
+	nlmsg_report_cookie(npt, nla);
+}
+
 static const struct nlattr_parser *
 search_states(const struct nlattr_parser *ps, int pslen, int key)
 {
diff --git a/sys/netlink/netlink_message_parser.h b/sys/netlink/netlink_message_parser.h
index 94f0ca5260d7..083c93dcbf8d 100644
--- a/sys/netlink/netlink_message_parser.h
+++ b/sys/netlink/netlink_message_parser.h
@@ -71,6 +71,7 @@ struct nl_pstate {
 	uint32_t		err_off;	/* error offset from hdr start */
         int			error;		/* last operation error */
 	char			*err_msg;	/* Description of last error */
+	struct nlattr		*cookie;	/* NLA to return to the userspace */
 	bool			strict;		/* Strict parsing required */
 };
 
@@ -198,6 +199,9 @@ bool nlmsg_report_err_msg(struct nl_pstate *npt, const char *fmt, ...);
 
 bool nlmsg_report_err_offset(struct nl_pstate *npt, uint32_t off);
 
+void nlmsg_report_cookie(struct nl_pstate *npt, struct nlattr *nla);
+void nlmsg_report_cookie_u32(struct nl_pstate *npt, uint32_t val);
+
 /*
  * Have it inline so compiler can optimize field accesses into
  * the list of direct function calls without iteration.
diff --git a/sys/netlink/netlink_message_writer.c b/sys/netlink/netlink_message_writer.c
index 2187c40f2786..8a9315eedd1b 100644
--- a/sys/netlink/netlink_message_writer.c
+++ b/sys/netlink/netlink_message_writer.c
@@ -643,10 +643,6 @@ nlmsg_ack(struct nlpcb *nlp, int error, struct nlmsghdr *hdr,
 	if ((npt->err_msg || npt->err_off) && nlp->nl_flags & NLF_EXT_ACK)
 		nl_flags |= NLM_F_ACK_TLVS;
 
-	/*
-	 * TODO: handle cookies
-	 */
-
 	NL_LOG(LOG_DEBUG3, "acknowledging message type %d seq %d",
 	    hdr->nlmsg_type, hdr->nlmsg_seq);
 
@@ -662,6 +658,8 @@ nlmsg_ack(struct nlpcb *nlp, int error, struct nlmsghdr *hdr,
 		nlattr_add_string(nw, NLMSGERR_ATTR_MSG, npt->err_msg);
 	if (npt->err_off != 0 && nlp->nl_flags & NLF_EXT_ACK)
 		nlattr_add_u32(nw, NLMSGERR_ATTR_OFFS, npt->err_off);
+	if (npt->cookie != NULL)
+		nlattr_add_raw(nw, npt->cookie);
 
 	if (nlmsg_end(nw))
 		return;
diff --git a/sys/netlink/netlink_message_writer.h b/sys/netlink/netlink_message_writer.h
index 99f50fb94213..bb4bb759251a 100644
--- a/sys/netlink/netlink_message_writer.h
+++ b/sys/netlink/netlink_message_writer.h
@@ -163,6 +163,27 @@ _nlmsg_reserve_attr(struct nl_writer *nw, uint16_t nla_type, uint16_t sz)
 }
 #define	nlmsg_reserve_attr(_ns, _at, _t)	((_t *)_nlmsg_reserve_attr(_ns, _at, NLA_ALIGN(sizeof(_t))))
 
+static inline bool
+nlattr_add_nla(struct nl_writer *nw, const struct nlattr *nla_src)
+{
+	MPASS(nla_src->nla_len >= sizeof(struct nlattr));
+
+	int required_len = NLA_ALIGN(nla_src->nla_len);
+        if (__predict_false(nw->offset + required_len > nw->alloc_len)) {
+		if (!nlmsg_refill_buffer(nw, required_len))
+			return (false);
+	}
+
+        struct nlattr *nla = (struct nlattr *)(&nw->data[nw->offset]);
+	if ((nla_src->nla_len % 4) != 0) {
+		/* clear padding bytes */
+		bzero((char *)nla + nla_src->nla_len - 4, 4);
+	}
+	memcpy(nla, nla_src, nla_src->nla_len);
+        nw->offset += required_len;
+	return (true);
+}
+
 static inline bool
 nlattr_add(struct nl_writer *nw, int attr_type, int attr_len, const void *data)
 {
@@ -188,6 +209,16 @@ nlattr_add(struct nl_writer *nw, int attr_type, int attr_len, const void *data)
         return (true);
 }
 
+static inline bool
+nlattr_add_raw(struct nl_writer *nw, const struct nlattr *nla_src)
+{
+	int attr_len = nla_src->nla_len - sizeof(struct nlattr);
+
+	MPASS(attr_len >= 0);
+
+	return (nlattr_add(nw, nla_src->nla_type, attr_len, (const void *)(nla_src + 1)));
+}
+
 static inline bool
 nlattr_add_u8(struct nl_writer *nw, int attrtype, uint8_t value)
 {
diff --git a/sys/netlink/route/iface_drivers.c b/sys/netlink/route/iface_drivers.c
index 1b8c27bfca68..7cfaa5a6614b 100644
--- a/sys/netlink/route/iface_drivers.c
+++ b/sys/netlink/route/iface_drivers.c
@@ -109,6 +109,41 @@ modify_generic(struct ifnet *ifp, struct nl_parsed_link *lattrs,
 	return (0);
 }
 
+/*
+ * Saves the resulting ifindex and ifname to report them
+ *  to userland along with the operation result.
+ * NLA format:
+ * NLMSGERR_ATTR_COOKIE(nested)
+ *  IFLA_NEW_IFINDEX(u32)
+ *  IFLA_IFNAME(string)
+ */
+static void
+store_cookie(struct nl_pstate *npt, struct ifnet *ifp)
+{
+	int ifname_len = strlen(if_name(ifp));
+	uint32_t ifindex = (uint32_t)ifp->if_index;
+
+	int nla_len = sizeof(struct nlattr) * 3 +
+		sizeof(ifindex) + NL_ITEM_ALIGN(ifname_len + 1);
+	struct nlattr *nla_cookie = npt_alloc(npt, nla_len);
+
+	/* Nested TLV */
+	nla_cookie->nla_len = nla_len;
+	nla_cookie->nla_type = NLMSGERR_ATTR_COOKIE;
+
+	struct nlattr *nla = nla_cookie + 1;
+	nla->nla_len = sizeof(struct nlattr) + sizeof(ifindex);
+	nla->nla_type = IFLA_NEW_IFINDEX;
+	memcpy(NLA_DATA(nla), &ifindex, sizeof(ifindex));
+
+	nla = NLA_NEXT(nla);
+	nla->nla_len = sizeof(struct nlattr) + ifname_len + 1;
+	nla->nla_type = IFLA_IFNAME;
+	strlcpy(NLA_DATA(nla), if_name(ifp), ifname_len + 1);
+
+	nlmsg_report_cookie(npt, nla_cookie);
+}
+
 /*
  * Generic creation interface handler.
  * Responsible for creating interfaces w/o parameters and setting
@@ -135,6 +170,8 @@ create_generic(struct nl_parsed_link *lattrs, const struct nlattr_bmask *bm,
 		if (!success)
 			return (EINVAL);
 		error = modify_generic(ifp, lattrs, bm, nlp, npt);
+		if (error == 0)
+			store_cookie(npt, ifp);
 		if_rele(ifp);
 	}
 
diff --git a/tests/atf_python/sys/net/netlink.py b/tests/atf_python/sys/net/netlink.py
index 57c8582627cf..ba7d41c7cbf8 100644
--- a/tests/atf_python/sys/net/netlink.py
+++ b/tests/atf_python/sys/net/netlink.py
@@ -950,58 +950,68 @@ def prepare_attrs_map(attrs: List[AttrDescr]) -> Dict[str, Dict]:
     return ret
 
 
-rtnl_route_attrs = [
-    AttrDescr(RtattrType.RTA_DST, NlAttrIp),
-    AttrDescr(RtattrType.RTA_SRC, NlAttrIp),
-    AttrDescr(RtattrType.RTA_IIF, NlAttrIfindex),
-    AttrDescr(RtattrType.RTA_OIF, NlAttrIfindex),
-    AttrDescr(RtattrType.RTA_GATEWAY, NlAttrTable),
-    AttrDescr(RtattrType.RTA_VIA, NlAttrVia),
-    AttrDescr(RtattrType.RTA_NH_ID, NlAttrNhId),
-    AttrDescr(
-        RtattrType.RTA_METRICS,
-        NlAttrNested,
-        [
-            AttrDescr(NlRtaxType.RTAX_MTU, NlAttrU32),
-        ],
-    ),
-]
-
-nldone_attrs = []
-
-nlerr_attrs = [
-    AttrDescr(NlErrattrType.NLMSGERR_ATTR_MSG, NlAttrStr),
-    AttrDescr(NlErrattrType.NLMSGERR_ATTR_OFFS, NlAttrU32),
-]
-
-rtnl_ifla_attrs = [
-    AttrDescr(IflattrType.IFLA_ADDRESS, NlAttrMac),
-    AttrDescr(IflattrType.IFLA_BROADCAST, NlAttrMac),
-    AttrDescr(IflattrType.IFLA_IFNAME, NlAttrStr),
-    AttrDescr(IflattrType.IFLA_MTU, NlAttrU32),
-    AttrDescr(IflattrType.IFLA_PROMISCUITY, NlAttrU32),
-    AttrDescr(IflattrType.IFLA_OPERSTATE, NlAttrU8),
-    AttrDescr(IflattrType.IFLA_CARRIER, NlAttrU8),
-    AttrDescr(IflattrType.IFLA_IFALIAS, NlAttrStr),
-    AttrDescr(IflattrType.IFLA_STATS64, NlAttrIfStats),
-    AttrDescr(
-        IflattrType.IFLA_LINKINFO,
-        NlAttrNested,
-        [
-            AttrDescr(IflinkInfo.IFLA_INFO_KIND, NlAttrStr),
-            AttrDescr(IflinkInfo.IFLA_INFO_DATA, NlAttr),
-        ],
-    ),
-]
-
-rtnl_ifa_attrs = [
-    AttrDescr(IfattrType.IFA_ADDRESS, NlAttrIp),
-    AttrDescr(IfattrType.IFA_LOCAL, NlAttrIp),
-    AttrDescr(IfattrType.IFA_LABEL, NlAttrStr),
-    AttrDescr(IfattrType.IFA_BROADCAST, NlAttrIp),
-    AttrDescr(IfattrType.IFA_ANYCAST, NlAttrIp),
-    AttrDescr(IfattrType.IFA_FLAGS, NlAttrU32),
-]
+rtnl_route_attrs = prepare_attrs_map(
+    [
+        AttrDescr(RtattrType.RTA_DST, NlAttrIp),
+        AttrDescr(RtattrType.RTA_SRC, NlAttrIp),
+        AttrDescr(RtattrType.RTA_IIF, NlAttrIfindex),
+        AttrDescr(RtattrType.RTA_OIF, NlAttrIfindex),
+        AttrDescr(RtattrType.RTA_GATEWAY, NlAttrTable),
+        AttrDescr(RtattrType.RTA_VIA, NlAttrVia),
+        AttrDescr(RtattrType.RTA_NH_ID, NlAttrNhId),
+        AttrDescr(
+            RtattrType.RTA_METRICS,
+            NlAttrNested,
+            [
+                AttrDescr(NlRtaxType.RTAX_MTU, NlAttrU32),
+            ],
+        ),
+    ]
+)
+
+nldone_attrs = prepare_attrs_map([])
+
+nlerr_attrs = prepare_attrs_map(
+    [
+        AttrDescr(NlErrattrType.NLMSGERR_ATTR_MSG, NlAttrStr),
+        AttrDescr(NlErrattrType.NLMSGERR_ATTR_OFFS, NlAttrU32),
+        AttrDescr(NlErrattrType.NLMSGERR_ATTR_COOKIE, NlAttr),
+    ]
+)
+
+rtnl_ifla_attrs = prepare_attrs_map(
+    [
+        AttrDescr(IflattrType.IFLA_ADDRESS, NlAttrMac),
+        AttrDescr(IflattrType.IFLA_BROADCAST, NlAttrMac),
+        AttrDescr(IflattrType.IFLA_IFNAME, NlAttrStr),
+        AttrDescr(IflattrType.IFLA_MTU, NlAttrU32),
+        AttrDescr(IflattrType.IFLA_PROMISCUITY, NlAttrU32),
+        AttrDescr(IflattrType.IFLA_OPERSTATE, NlAttrU8),
+        AttrDescr(IflattrType.IFLA_CARRIER, NlAttrU8),
+        AttrDescr(IflattrType.IFLA_IFALIAS, NlAttrStr),
+        AttrDescr(IflattrType.IFLA_STATS64, NlAttrIfStats),
+        AttrDescr(IflattrType.IFLA_NEW_IFINDEX, NlAttrU32),
+        AttrDescr(
+            IflattrType.IFLA_LINKINFO,
+            NlAttrNested,
+            [
+                AttrDescr(IflinkInfo.IFLA_INFO_KIND, NlAttrStr),
+                AttrDescr(IflinkInfo.IFLA_INFO_DATA, NlAttr),
+            ],
+        ),
+    ]
+)
+
+rtnl_ifa_attrs = prepare_attrs_map(
+    [
+        AttrDescr(IfattrType.IFA_ADDRESS, NlAttrIp),
+        AttrDescr(IfattrType.IFA_LOCAL, NlAttrIp),
+        AttrDescr(IfattrType.IFA_LABEL, NlAttrStr),
+        AttrDescr(IfattrType.IFA_BROADCAST, NlAttrIp),
+        AttrDescr(IfattrType.IFA_ANYCAST, NlAttrIp),
+        AttrDescr(IfattrType.IFA_FLAGS, NlAttrU32),
+    ]
+)
 
 
 class BaseNetlinkMessage(object):
@@ -1140,7 +1150,7 @@ class StdNetlinkMessage(BaseNetlinkMessage):
             raise
         return self
 
-    def _parse_attrs(self, data: bytes, attr_map):
+    def parse_attrs(self, data: bytes, attr_map):
         ret = []
         off = 0
         while len(data) - off >= 4:
@@ -1157,7 +1167,7 @@ class StdNetlinkMessage(BaseNetlinkMessage):
                 val = v["ad"].cls.from_bytes(data[off : off + nla_len], v["ad"].val)
                 if "child" in v:
                     # nested
-                    attrs, _ = self._parse_attrs(data[off : off + nla_len], v["child"])
+                    attrs, _ = self.parse_attrs(data[off : off + nla_len], v["child"])
                     val = NlAttrNested(raw_nla_type, attrs)
             else:
                 # unknown attribute
@@ -1167,7 +1177,7 @@ class StdNetlinkMessage(BaseNetlinkMessage):
         return ret, off
 
     def parse_nla_list(self, data: bytes) -> List[NlAttr]:
-        return self._parse_attrs(data, self.nl_attrs_map)
+        return self.parse_attrs(data, self.nl_attrs_map)
 
     def print_message(self):
         self.print_nl_header(self.nl_hdr)
@@ -1178,7 +1188,7 @@ class StdNetlinkMessage(BaseNetlinkMessage):
 
 class NetlinkDoneMessage(StdNetlinkMessage):
     messages = [NlMsgType.NLMSG_DONE.value]
-    nl_attrs_map = prepare_attrs_map(nldone_attrs)
+    nl_attrs_map = nldone_attrs
 
     @property
     def error_code(self):
@@ -1197,7 +1207,7 @@ class NetlinkDoneMessage(StdNetlinkMessage):
 
 class NetlinkErrorMessage(StdNetlinkMessage):
     messages = [NlMsgType.NLMSG_ERROR.value]
-    nl_attrs_map = prepare_attrs_map(nlerr_attrs)
+    nl_attrs_map = nlerr_attrs
 
     @property
     def error_code(self):
@@ -1217,6 +1227,10 @@ class NetlinkErrorMessage(StdNetlinkMessage):
             return nla.u32
         return None
 
+    @property
+    def cookie(self):
+        return self.get_nla(NlErrattrType.NLMSGERR_ATTR_COOKIE)
+
     def parse_base_header(self, data):
         if len(data) < sizeof(Nlmsgerr):
             raise ValueError("length less than nlmsgerr header")
@@ -1257,7 +1271,7 @@ class NetlinkRtMessage(BaseNetlinkRtMessage):
         NlRtMsgType.RTM_DELROUTE.value,
         NlRtMsgType.RTM_GETROUTE.value,
     ]
-    nl_attrs_map = prepare_attrs_map(rtnl_route_attrs)
+    nl_attrs_map = rtnl_route_attrs
 
     def __init__(self, helper, nlm_type):
         super().__init__(helper, nlm_type)
@@ -1297,7 +1311,7 @@ class NetlinkIflaMessage(BaseNetlinkRtMessage):
         NlRtMsgType.RTM_DELLINK.value,
         NlRtMsgType.RTM_GETLINK.value,
     ]
-    nl_attrs_map = prepare_attrs_map(rtnl_ifla_attrs)
+    nl_attrs_map = rtnl_ifla_attrs
 
     def __init__(self, helper, nlm_type):
         super().__init__(helper, nlm_type)
@@ -1329,7 +1343,7 @@ class NetlinkIfaMessage(BaseNetlinkRtMessage):
         NlRtMsgType.RTM_DELADDR.value,
         NlRtMsgType.RTM_GETADDR.value,
     ]
-    nl_attrs_map = prepare_attrs_map(rtnl_ifa_attrs)
+    nl_attrs_map = rtnl_ifa_attrs
 
     def __init__(self, helper, nlm_type):
         super().__init__(helper, nlm_type)
diff --git a/tests/sys/netlink/test_rtnl_iface.py b/tests/sys/netlink/test_rtnl_iface.py
index 7cff592b1676..ecc932c6213e 100644
--- a/tests/sys/netlink/test_rtnl_iface.py
+++ b/tests/sys/netlink/test_rtnl_iface.py
@@ -17,6 +17,7 @@ from atf_python.sys.net.netlink import NlmBaseFlags
 from atf_python.sys.net.netlink import NlmNewFlags
 from atf_python.sys.net.netlink import NlMsgType
 from atf_python.sys.net.netlink import NlRtMsgType
+from atf_python.sys.net.netlink import rtnl_ifla_attrs
 from atf_python.sys.net.vnet import SingleVnetTestTemplate
 
 
@@ -91,6 +92,40 @@ class TestRtNlIface(NetlinkTestTemplate, SingleVnetTestTemplate):
 
         self.get_interface_byname("lo10")
 
+    @pytest.mark.require_user("root")
+    def test_create_iface_plain_retvals(self):
+        """Tests loopback creation w/o any parameters"""
+        flags = NlmNewFlags.NLM_F_EXCL.value | NlmNewFlags.NLM_F_CREATE.value
+        msg = NetlinkIflaMessage(self.helper, NlRtMsgType.RTM_NEWLINK.value)
+        msg.nl_hdr.nlmsg_flags = (
+            flags | NlmBaseFlags.NLM_F_ACK.value | NlmBaseFlags.NLM_F_REQUEST.value
+        )
+        msg.add_nla(NlAttrStr(IflattrType.IFLA_IFNAME, "lo10"))
+        msg.add_nla(
+            NlAttrNested(
+                IflattrType.IFLA_LINKINFO,
+                [
+                    NlAttrStrn(IflinkInfo.IFLA_INFO_KIND, "lo"),
+                ],
+            )
+        )
+
+        rx_msg = self.get_reply(msg)
+        assert rx_msg.is_type(NlMsgType.NLMSG_ERROR)
+        assert rx_msg.error_code == 0
+        assert rx_msg.cookie is not None
+        nla_list, _ = rx_msg.parse_attrs(bytes(rx_msg.cookie)[4:], rtnl_ifla_attrs)
+        nla_map = {n.nla_type: n for n in nla_list}
+        assert IflattrType.IFLA_IFNAME.value in nla_map
+        assert nla_map[IflattrType.IFLA_IFNAME.value].text == "lo10"
+        assert IflattrType.IFLA_NEW_IFINDEX.value in nla_map
+        assert nla_map[IflattrType.IFLA_NEW_IFINDEX.value].u32 > 0
+
+        lo_msg = self.get_interface_byname("lo10")
+        assert (
+            lo_msg.base_hdr.ifi_index == nla_map[IflattrType.IFLA_NEW_IFINDEX.value].u32
+        )
+
     @pytest.mark.require_user("root")
     def test_create_iface_attrs(self):
         """Tests interface creation with additional properties"""