David Ahern wrote:

On 1/30/18 11:09 AM, Serhey Popovych wrote:

quoted

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 051a05f..f8fd392 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c

@@ -948,14 +948,14 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
 	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
 	if (tb[IFLA_IFNAME] == NULL) {
 		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n", ifi->ifi_index);
-		name = "<nil>";
+		name = ll_index_to_name(ifi->ifi_index);

This is one of those "should never happen checks" since the kernel
always adds IFLA_IFNAME. Going to a cache to get a name for the index
when the existing message is missing that attribute seems wrong. I
realize the expectation is that the cache is empty today so if%d is
returned, but that could change and it is the idea of consulting a cache
that I think is wrong.

If that intention is to have a name I think it is safer to just have it
set to if%d here (or in a helper that the cache also uses).

In my opinion in print_*() functions it is expected that cache isn't
empty. That's actually point where we benefit from cache.

I understand side effects this change may introduce and your concerns
about them. Will present small set of changes to export "if%d" template
from lib/ll_map.c for use here.

Using "<nil>" of something other, even for "should never happen" case
seems wrong to me.

quoted

 	} else {
 		name = rta_getattr_str(tb[IFLA_IFNAME]);
 	}
 
 	if (pfilter->label &&
 	    (!pfilter->family || pfilter->family == AF_PACKET) &&
-	    fnmatch(pfilter->label, RTA_DATA(tb[IFLA_IFNAME]), 0))
+	    fnmatch(pfilter->label, name, 0))
 		return -1;
 
 	if (tb[IFLA_GROUP]) {

@@ -1057,6 +1057,7 @@ int print_linkinfo(const struct sockaddr_nl *who,
 	struct ifinfomsg *ifi = NLMSG_DATA(n);
 	struct rtattr *tb[IFLA_MAX+1];
 	int len = n->nlmsg_len;
+	const char *name;
 	unsigned int m_flag = 0;
 
 	if (n->nlmsg_type != RTM_NEWLINK && n->nlmsg_type != RTM_DELLINK)

@@ -1067,18 +1068,22 @@ int print_linkinfo(const struct sockaddr_nl *who,
 		return -1;
 
 	if (filter.ifindex && ifi->ifi_index != filter.ifindex)
-		return 0;
+		return -1;
 	if (filter.up && !(ifi->ifi_flags&IFF_UP))
-		return 0;
+		return -1;
 
 	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
-	if (tb[IFLA_IFNAME] == NULL)
+	if (tb[IFLA_IFNAME] == NULL) {
 		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n", ifi->ifi_index);
+		name = ll_index_to_name(ifi->ifi_index);

same here

quoted

+	} else {
+		name = rta_getattr_str(tb[IFLA_IFNAME]);
+	}
 
 	if (filter.label &&
 	    (!filter.family || filter.family == AF_PACKET) &&
-	    fnmatch(filter.label, RTA_DATA(tb[IFLA_IFNAME]), 0))
-		return 0;
+	    fnmatch(filter.label, name, 0))
+		return -1;
 
 	if (tb[IFLA_GROUP]) {
 		int group = rta_getattr_u32(tb[IFLA_GROUP]);

@@ -1105,16 +1110,7 @@ int print_linkinfo(const struct sockaddr_nl *who,
 		print_bool(PRINT_ANY, "deleted", "Deleted ", true);
 
 	print_int(PRINT_ANY, "ifindex", "%d: ", ifi->ifi_index);
-	if (tb[IFLA_IFNAME]) {
-		print_color_string(PRINT_ANY,
-				   COLOR_IFNAME,
-				   "ifname", "%s",
-				   rta_getattr_str(tb[IFLA_IFNAME]));
-	} else {
-		print_null(PRINT_JSON, "ifname", NULL, NULL);
-		print_color_null(PRINT_FP, COLOR_IFNAME,
-				 "ifname", "%s", "<nil>");
-	}
+	print_color_string(PRINT_ANY, COLOR_IFNAME, "ifname", "%s", name);
 
 	if (tb[IFLA_LINK]) {
 		int iflink = rta_getattr_u32(tb[IFLA_LINK]);