[PATCH iproute2-next v5 7/9] utils: Introduce and use get_ifname_rta()

[Serhey Popovych <serhe.popovych@gmail.com>]

Be consistent in handling of IFLA_IFNAME attribute in all places: if
there is no attribute report bug to stderr and use ll_idx_n2a() as
last measure to get name in "if%u" format instead of "<nil>".

Use check_ifname() to validate network device name: this catches both
unexpected return from kernel and ll_idx_n2a().

Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>
---
 bridge/link.c   |    8 ++++----
 include/utils.h |    1 +
 ip/ipaddress.c  |   20 ++++++++------------
 lib/utils.c     |   19 +++++++++++++++++++
 4 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/bridge/link.c b/bridge/link.c
index 870ebe0..a11cbb1 100644
--- a/bridge/link.c
+++ b/bridge/link.c
@@ -99,9 +99,10 @@ int print_linkinfo(const struct sockaddr_nl *who,
 		   struct nlmsghdr *n, void *arg)
 {
 	FILE *fp = arg;
-	int len = n->nlmsg_len;
 	struct ifinfomsg *ifi = NLMSG_DATA(n);
 	struct rtattr *tb[IFLA_MAX+1];
+	int len = n->nlmsg_len;
+	const char *name;
 
 	len -= NLMSG_LENGTH(sizeof(*ifi));
 	if (len < 0) {
@@ -117,10 +118,9 @@ int print_linkinfo(const struct sockaddr_nl *who,
 
 	parse_rtattr_flags(tb, IFLA_MAX, IFLA_RTA(ifi), len, NLA_F_NESTED);
 
-	if (tb[IFLA_IFNAME] == NULL) {
-		fprintf(stderr, "BUG: nil ifname\n");
+	name = get_ifname_rta(ifi->ifi_index, tb[IFLA_IFNAME]);
+	if (!name)
 		return -1;
-	}
 
 	if (n->nlmsg_type == RTM_DELLINK)
 		fprintf(fp, "Deleted ");
diff --git a/include/utils.h b/include/utils.h
index 867e540..84ca873 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -183,6 +183,7 @@ void duparg(const char *, const char *) __attribute__((noreturn));
 void duparg2(const char *, const char *) __attribute__((noreturn));
 int check_ifname(const char *);
 int get_ifname(char *, const char *);
+const char *get_ifname_rta(int ifindex, const struct rtattr *rta);
 int matches(const char *arg, const char *pattern);
 int inet_addr_match(const inet_prefix *a, const inet_prefix *b, int bits);
 int inet_addr_match_rta(const inet_prefix *m, const struct rtattr *rta);
diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 749178d..08d2576 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -776,12 +776,10 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
 		return -1;
 
 	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 = ll_idx_n2a(ifi->ifi_index);
-	} else {
-		name = rta_getattr_str(tb[IFLA_IFNAME]);
-	}
+
+	name = get_ifname_rta(ifi->ifi_index, tb[IFLA_IFNAME]);
+	if (!name)
+		return -1;
 
 	if (filter.label &&
 	    (!filter.family || filter.family == AF_PACKET) &&
@@ -903,12 +901,10 @@ int print_linkinfo(const struct sockaddr_nl *who,
 		return -1;
 
 	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 = ll_idx_n2a(ifi->ifi_index);
-	} else {
-		name = rta_getattr_str(tb[IFLA_IFNAME]);
-	}
+
+	name = get_ifname_rta(ifi->ifi_index, tb[IFLA_IFNAME]);
+	if (!name)
+		return -1;
 
 	if (filter.label &&
 	    (!filter.family || filter.family == AF_PACKET) &&
diff --git a/lib/utils.c b/lib/utils.c
index d86c2ee..572d42a 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -871,6 +871,25 @@ int get_ifname(char *buf, const char *name)
 	return ret;
 }
 
+const char *get_ifname_rta(int ifindex, const struct rtattr *rta)
+{
+	const char *name;
+
+	if (rta) {
+		name = rta_getattr_str(rta);
+	} else {
+		fprintf(stderr,
+			"BUG: device with ifindex %d has nil ifname\n",
+			ifindex);
+		name = ll_idx_n2a(ifindex);
+	}
+
+	if (check_ifname(name))
+		return NULL;
+
+	return name;
+}
+
 int matches(const char *cmd, const char *pattern)
 {
 	int len = strlen(cmd);
-- 
1.7.10.4