xtables-translate: Fix for interface name corner-cases

There are two special situations xlate_ifname() didn't cover for:

* Interface name containing '*': This went unchanged, creating a command
  nft wouldn't accept. Instead translate into '\*' which doesn't change
  semantics.

* Interface name being '+': Can't translate into nft wildcard character
  as nft doesn't accept asterisk-only interface names. Instead decide
  what to do based on 'invert' value: Skip match creation if false,
  match against an invalid interface name if true.

Also add a test to make sure future changes to this behaviour are
noticed.

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

diff --git a/extensions/generic.txlate b/extensions/generic.txlate
index b38fbd1fe113ba6992242e3641910666534f2d70..c92d082abea7834f12d8b2fdbeda9a2a55b7bb87 100644 (file)
--- a/extensions/generic.txlate
+++ b/extensions/generic.txlate
@@ -18,3 +18,15 @@ nft add rule bridge filter FORWARD iifname != "iname" meta ibrname "ilogname" oi
 
 ebtables-translate -I INPUT -p ip -d 1:2:3:4:5:6/ff:ff:ff:ff:00:00
 nft insert rule bridge filter INPUT ether type 0x800 ether daddr 01:02:03:04:00:00 and ff:ff:ff:ff:00:00 == 01:02:03:04:00:00 counter
+
+# asterisk is not special in iptables and it is even a valid interface name
+iptables-translate -A FORWARD -i '*' -o 'eth*foo'
+nft add rule ip filter FORWARD iifname "\*" oifname "eth\*foo" counter
+
+# skip for always matching interface names
+iptables-translate -A FORWARD -i '+'
+nft add rule ip filter FORWARD counter
+
+# match against invalid interface name to simulate never matching rule
+iptables-translate -A FORWARD ! -i '+'
+nft add rule ip filter FORWARD iifname "INVAL/D" counter

diff --git a/iptables/xtables-translate.c b/iptables/xtables-translate.c
index 77a186b905d73686f530891d4c406cad0608c8ea..c4e177c0d63ba1bc44416ee77fe4987f3d5bfa70 100644 (file)
--- a/iptables/xtables-translate.c
+++ b/iptables/xtables-translate.c
@@ -32,15 +32,38 @@
 void xlate_ifname(struct xt_xlate *xl, const char *nftmeta, const char *ifname,
                  bool invert)
 {
-       int ifaclen = strlen(ifname);
-       char iface[IFNAMSIZ];
+       int ifaclen = strlen(ifname), i, j;
+       char iface[IFNAMSIZ * 2];
 
        if (ifaclen < 1 || ifaclen >= IFNAMSIZ)
                return;
 
-       strcpy(iface, ifname);
-       if (iface[ifaclen - 1] == '+')
-               iface[ifaclen - 1] = '*';
+       for (i = 0, j = 0; i < ifaclen + 1; i++, j++) {
+               switch (ifname[i]) {
+               case '+':
+                       iface[j] = '*';
+                       break;
+               case '*':
+                       iface[j++] = '\\';
+                       /* fall through */
+               default:
+                       iface[j] = ifname[i];
+                       break;
+               }
+       }
+
+       if (ifaclen == 1 && ifname[0] == '+') {
+               /* Nftables does not support wildcard only string. Workaround
+                * is easy, given that this will match always or never
+                * depending on 'invert' value. To match always, simply don't
+                * generate an expression. To match never, use an invalid
+                * interface name (kernel doesn't accept '/' in names) to match
+                * against. */
+               if (!invert)
+                       return;
+               strcpy(iface, "INVAL/D");
+               invert = false;
+       }
 
        xt_xlate_add(xl, "%s %s\"%s\" ", nftmeta, invert ? "!= " : "", iface);
 }