segtree: don't remove nul-root element from interval set

Check from the delinearize set element path if the nul-root element
already exists in the interval set. Hence, the element insertion path
skips the implicit nul-root interval insertion.

Under some circunstances, nft bogusly fails to delete the last element
of the interval set and to create an element in an existing empty
internal set. This patch includes a test that reproduces the issue.

Fixes: 4935a0d561b5 ("segtree: special handling for the first non-matching segment")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/tests/shell/testcases/sets/0041interval_0 b/tests/shell/testcases/sets/0041interval_0
new file mode 100755
index 00000000..42fc6ccf
--- /dev/null
+++ b/tests/shell/testcases/sets/0041interval_0
@@ -0,0 +1,25 @@
+#!/bin/bash
+
+set -e
+
+RULESET="
+table ip t {
+        set s {
+                type ipv4_addr
+                flags interval
+                elements = { 192.168.2.195, 192.168.2.196,
+                             192.168.2.197, 192.168.2.198 }
+        }
+}"
+
+$NFT -f - <<< "$RULESET"
+
+$NFT 'delete element t s { 192.168.2.195, 192.168.2.196 }; add element t s { 192.168.2.196 }' 2>/dev/null
+$NFT get element t s { 192.168.2.196, 192.168.2.197, 192.168.2.198 } 1>/dev/null
+$NFT 'delete element t s { 192.168.2.196, 192.168.2.197 }; add element t s { 192.168.2.197 }' 2>/dev/null
+$NFT get element t s { 192.168.2.197, 192.168.2.198 } 1>/dev/null
+$NFT 'delete element t s { 192.168.2.198, 192.168.2.197 }; add element t s { 192.168.2.196, 192.168.2.197, 192.168.2.195 }' 1>/dev/null
+$NFT get element t s { 192.168.2.196, 192.168.2.197, 192.168.2.195 } 1>/dev/null
+$NFT delete element t s { 192.168.2.196, 192.168.2.197, 192.168.2.195 } 2>/dev/null
+$NFT create element t s { 192.168.2.196} 2>/dev/null
+$NFT get element t s { 192.168.2.196 } 1>/dev/null