utils: Add helpers for interface name wildcards

Support simple (suffix) wildcards in NFTNL_{CHAIN,FLOWTABLE}_DEVICES
identified by NFTA_DEVICE_PREFIX attribute. Add helpers converting to
and from the human-readable asterisk-suffix notation.

Signed-off-by: Phil Sutter <phil@nwl.cc>

4 files changed, 50 insertions, 5 deletions

diff --git a/src/chain.c b/src/chain.c
index 895108c..8396114 100644
--- a/src/chain.c
+++ b/src/chain.c
@@ -464,7 +464,7 @@ void nftnl_chain_nlmsg_build_payload(struct nlmsghdr *nlh, const struct nftnl_ch
 
 		nest_dev = mnl_attr_nest_start(nlh, NFTA_HOOK_DEVS);
 		nftnl_str_array_foreach(dev, &c->dev_array, i)
-			mnl_attr_put_strz(nlh, NFTA_DEVICE_NAME, dev);
+			nftnl_attr_put_ifname(nlh, dev);
 		mnl_attr_nest_end(nlh, nest_dev);
 	}
 
@@ -648,6 +648,8 @@ static int nftnl_chain_parse_hook(struct nlattr *attr, struct nftnl_chain *c)
 		c->flags |= (1 << NFTNL_CHAIN_PRIO);
 	}
 	if (tb[NFTA_HOOK_DEV]) {
+		if (c->flags & (1 << NFTNL_CHAIN_DEV))
+			xfree(c->dev);
 		c->dev = strdup(mnl_attr_get_str(tb[NFTA_HOOK_DEV]));
 		if (!c->dev)
 			return -1;
diff --git a/src/flowtable.c b/src/flowtable.c
index fbbe0a8..59991d6 100644
--- a/src/flowtable.c
+++ b/src/flowtable.c
@@ -299,7 +299,7 @@ void nftnl_flowtable_nlmsg_build_payload(struct nlmsghdr *nlh,
 
 		nest_dev = mnl_attr_nest_start(nlh, NFTA_FLOWTABLE_HOOK_DEVS);
 		nftnl_str_array_foreach(dev, &c->dev_array, i)
-			mnl_attr_put_strz(nlh, NFTA_DEVICE_NAME, dev);
+			nftnl_attr_put_ifname(nlh, dev);
 		mnl_attr_nest_end(nlh, nest_dev);
 	}
 
diff --git a/src/str_array.c b/src/str_array.c
index 5669c61..4292c98 100644
--- a/src/str_array.c
+++ b/src/str_array.c
@@ -45,9 +45,13 @@ int nftnl_parse_devs(struct nftnl_str_array *sa, const struct nlattr *nest)
 	int len = 0;
 
 	mnl_attr_for_each_nested(attr, nest) {
-		if (mnl_attr_get_type(attr) != NFTA_DEVICE_NAME)
+		switch(mnl_attr_get_type(attr)) {
+		default:
 			return -1;
-		len++;
+		case NFTA_DEVICE_NAME:
+		case NFTA_DEVICE_PREFIX:
+			len++;
+		}
 	}
 
 	nftnl_str_array_clear(sa);
@@ -56,7 +60,7 @@ int nftnl_parse_devs(struct nftnl_str_array *sa, const struct nlattr *nest)
 		return -1;
 
 	mnl_attr_for_each_nested(attr, nest) {
-		sa->array[sa->len] = strdup(mnl_attr_get_str(attr));
+		sa->array[sa->len] = nftnl_attr_get_ifname(attr);
 		if (!sa->array[sa->len]) {
 			nftnl_str_array_clear(sa);
 			return -1;
diff --git a/src/utils.c b/src/utils.c
index 5f2c5bf..c4bbd4f 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -13,8 +13,11 @@
 #include <errno.h>
 #include <inttypes.h>
 
+#include <libmnl/libmnl.h>
+
 #include <libnftnl/common.h>
 
+#include <linux/if.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter/nf_tables.h>
 
@@ -146,3 +149,39 @@ int nftnl_set_str_attr(const char **dptr, uint32_t *flags,
 	*flags |= (1 << attr);
 	return 0;
 }
+
+static bool is_wildcard_str(const char *str)
+{
+	size_t len = strlen(str);
+
+	if (len < 1 || str[len - 1] != '*')
+		return false;
+	if (len < 2 || str[len - 2] != '\\')
+		return true;
+	/* XXX: ignore backslash escaping for now */
+	return false;
+}
+
+void nftnl_attr_put_ifname(struct nlmsghdr *nlh, const char *ifname)
+{
+	uint16_t attr = is_wildcard_str(ifname) ?
+			NFTA_DEVICE_PREFIX : NFTA_DEVICE_NAME;
+
+	mnl_attr_put_strz(nlh, attr, ifname);
+}
+
+char *nftnl_attr_get_ifname(const struct nlattr *attr)
+{
+	const char *dev = mnl_attr_get_str(attr);
+	char buf[IFNAMSIZ];
+
+	switch (mnl_attr_get_type(attr)) {
+	case NFTA_DEVICE_NAME:
+		return strdup(dev);
+	case NFTA_DEVICE_PREFIX:
+		snprintf(buf, IFNAMSIZ, "%s*", dev);
+		return strdup(buf);
+	default:
+		return NULL;
+	}
+}