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From da36213a48f6114ab998a5fb37bae61d2a02d5f6 Mon Sep 17 00:00:00 2001
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From: Phil Sutter <phil@nwl.cc>
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Date: Thu, 6 Feb 2020 15:08:41 +0100
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Subject: [PATCH] xtables-translate: Fix for interface name corner-cases
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There are two special situations xlate_ifname() didn't cover for:
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* Interface name containing '*': This went unchanged, creating a command
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nft wouldn't accept. Instead translate into '\*' which doesn't change
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semantics.
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* Interface name being '+': Can't translate into nft wildcard character
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as nft doesn't accept asterisk-only interface names. Instead decide
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what to do based on 'invert' value: Skip match creation if false,
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match against an invalid interface name if true.
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Also add a test to make sure future changes to this behaviour are
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noticed.
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Signed-off-by: Phil Sutter <phil@nwl.cc>
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(cherry picked from commit e179e87a1179e272a9bdabb0220b17d61d099ee3)
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Signed-off-by: Phil Sutter <psutter@redhat.com>
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---
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extensions/generic.txlate | 12 ++++++++++++
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iptables/xtables-translate.c | 33 ++++++++++++++++++++++++++++-----
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2 files changed, 40 insertions(+), 5 deletions(-)
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diff --git a/extensions/generic.txlate b/extensions/generic.txlate
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index b38fbd1fe113b..c92d082abea78 100644
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--- a/extensions/generic.txlate
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+++ b/extensions/generic.txlate
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@@ -18,3 +18,15 @@ nft add rule bridge filter FORWARD iifname != "iname" meta ibrname "ilogname" oi
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ebtables-translate -I INPUT -p ip -d 1:2:3:4:5:6/ff:ff:ff:ff:00:00
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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
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+
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+# asterisk is not special in iptables and it is even a valid interface name
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+iptables-translate -A FORWARD -i '*' -o 'eth*foo'
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+nft add rule ip filter FORWARD iifname "\*" oifname "eth\*foo" counter
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+
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+# skip for always matching interface names
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+iptables-translate -A FORWARD -i '+'
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+nft add rule ip filter FORWARD counter
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+
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+# match against invalid interface name to simulate never matching rule
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+iptables-translate -A FORWARD ! -i '+'
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+nft add rule ip filter FORWARD iifname "INVAL/D" counter
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diff --git a/iptables/xtables-translate.c b/iptables/xtables-translate.c
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index 77a186b905d73..c4e177c0d63ba 100644
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--- a/iptables/xtables-translate.c
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+++ b/iptables/xtables-translate.c
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@@ -32,15 +32,38 @@
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void xlate_ifname(struct xt_xlate *xl, const char *nftmeta, const char *ifname,
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bool invert)
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{
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- int ifaclen = strlen(ifname);
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- char iface[IFNAMSIZ];
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+ int ifaclen = strlen(ifname), i, j;
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+ char iface[IFNAMSIZ * 2];
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if (ifaclen < 1 || ifaclen >= IFNAMSIZ)
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return;
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- strcpy(iface, ifname);
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- if (iface[ifaclen - 1] == '+')
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- iface[ifaclen - 1] = '*';
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+ for (i = 0, j = 0; i < ifaclen + 1; i++, j++) {
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+ switch (ifname[i]) {
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+ case '+':
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+ iface[j] = '*';
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+ break;
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+ case '*':
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+ iface[j++] = '\\';
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+ /* fall through */
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+ default:
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+ iface[j] = ifname[i];
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+ break;
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+ }
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+ }
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+
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+ if (ifaclen == 1 && ifname[0] == '+') {
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+ /* Nftables does not support wildcard only string. Workaround
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+ * is easy, given that this will match always or never
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+ * depending on 'invert' value. To match always, simply don't
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+ * generate an expression. To match never, use an invalid
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+ * interface name (kernel doesn't accept '/' in names) to match
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+ * against. */
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+ if (!invert)
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+ return;
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+ strcpy(iface, "INVAL/D");
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+ invert = false;
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+ }
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xt_xlate_add(xl, "%s %s\"%s\" ", nftmeta, invert ? "!= " : "", iface);
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}
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--
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2.24.1
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