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Thu, 06 Aug 2026 11:50:28 -0700 (PDT) Received: from localhost.localdomain ([102.135.242.143]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4995c69c8ffsm567865e9.2.2026.08.06.11.50.25 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 06 Aug 2026 11:50:27 -0700 (PDT) From: Adrian Moisey To: netfilter-devel@vger.kernel.org Cc: Adrian Moisey Subject: [PATCH nft] netlink_linearize: size nat register allocation by address expression Date: Thu, 6 Aug 2026 20:50:20 +0200 Message-ID: <20260806185020.95154-1-adrian@changeover.za.net> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit nat statements with a literal concatenation of address and port, e.g. dnat ip6 addr . port to fd00:10:244::4 . 6443 allocated a fixed 128-bit register block for the address, but the ip6 address . port concatenation is 144 bits (5 registers), so netlink_gen_concat overran into unallocated registers and hit the assertion 'dreg < ctx->reg_low' in netlink_gen_expr. IPv4 escaped by luck since its 48-bit concatenation fits into the padded block. Allocate the register based on the address expression instead, which sizes by expr->len for concatenations, and add the matching release_register() call. Extend the nat_addr_port test with literal concatenation rules for ip and ip6. Signed-off-by: Adrian Moisey --- src/netlink_linearize.c | 6 ++- .../maps/dumps/nat_addr_port.json-nft | 54 +++++++++++++++++++ .../testcases/maps/dumps/nat_addr_port.nft | 2 + tests/shell/testcases/maps/nat_addr_port | 2 + 4 files changed, 62 insertions(+), 2 deletions(-) diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c index ac0eaff9..dfa841c6 100644 --- a/src/netlink_linearize.c +++ b/src/netlink_linearize.c @@ -1292,8 +1292,7 @@ static void netlink_gen_nat_stmt(struct netlink_linearize_ctx *ctx, nftnl_expr_set_u32(nle, nftnl_flag_attr, stmt->nat.flags); if (stmt->nat.addr) { - amin_reg = get_register(ctx, NULL); - registers++; + amin_reg = get_register(ctx, stmt->nat.addr); if (stmt->nat.addr->etype == EXPR_RANGE) { amax_reg = get_register(ctx, NULL); @@ -1374,6 +1373,9 @@ static void netlink_gen_nat_stmt(struct netlink_linearize_ctx *ctx, registers--; } + if (stmt->nat.addr) + release_register(ctx, stmt->nat.addr); + nft_rule_add_expr(ctx, nle, &stmt->location); } diff --git a/tests/shell/testcases/maps/dumps/nat_addr_port.json-nft b/tests/shell/testcases/maps/dumps/nat_addr_port.json-nft index 38b01e69..09052c43 100644 --- a/tests/shell/testcases/maps/dumps/nat_addr_port.json-nft +++ b/tests/shell/testcases/maps/dumps/nat_addr_port.json-nft @@ -320,6 +320,33 @@ ] } }, + { + "rule": { + "family": "ip", + "table": "ipfoo", + "chain": "c", + "handle": 0, + "expr": [ + { + "match": { + "op": "==", + "left": { + "meta": { + "key": "l4proto" + } + }, + "right": "tcp" + } + }, + { + "dnat": { + "addr": "10.2.3.4", + "port": 4242 + } + } + ] + } + }, { "rule": { "family": "ip", @@ -670,6 +697,33 @@ ] } }, + { + "rule": { + "family": "ip6", + "table": "ip6foo", + "chain": "c", + "handle": 0, + "expr": [ + { + "match": { + "op": "==", + "left": { + "meta": { + "key": "l4proto" + } + }, + "right": "tcp" + } + }, + { + "dnat": { + "addr": "fd00:10:244::4", + "port": 6443 + } + } + ] + } + }, { "rule": { "family": "ip6", diff --git a/tests/shell/testcases/maps/dumps/nat_addr_port.nft b/tests/shell/testcases/maps/dumps/nat_addr_port.nft index c8493b3a..fb1c190a 100644 --- a/tests/shell/testcases/maps/dumps/nat_addr_port.nft +++ b/tests/shell/testcases/maps/dumps/nat_addr_port.nft @@ -29,6 +29,7 @@ table ip ipfoo { ip saddr 10.1.1.2 tcp dport 42 dnat to 10.2.3.4:4242 meta l4proto tcp dnat ip to ip saddr map @y dnat ip to ip saddr . tcp dport map @z + meta l4proto tcp dnat to 10.2.3.4:4242 dnat to numgen inc mod 2 map @t1 meta l4proto tcp dnat ip to numgen inc mod 2 map @t2 } @@ -62,6 +63,7 @@ table ip6 ip6foo { ip6 saddr dead::2 tcp dport 42 dnat to [c0::1a]:4242 meta l4proto tcp dnat ip6 to ip6 saddr map @y dnat ip6 to ip6 saddr . tcp dport map @z + meta l4proto tcp dnat to [fd00:10:244::4]:6443 dnat to numgen inc mod 2 map @t1 meta l4proto tcp dnat ip6 to numgen inc mod 2 map @t2 } diff --git a/tests/shell/testcases/maps/nat_addr_port b/tests/shell/testcases/maps/nat_addr_port index 703a2ad9..5f6ff1c4 100755 --- a/tests/shell/testcases/maps/nat_addr_port +++ b/tests/shell/testcases/maps/nat_addr_port @@ -31,6 +31,7 @@ table ip ipfoo { ip saddr 10.1.1.2 tcp dport 42 dnat to 10.2.3.4:4242 meta l4proto tcp dnat ip addr . port to ip saddr map @y meta l4proto tcp dnat ip addr . port to ip saddr . tcp dport map @z + meta l4proto tcp dnat ip addr . port to 10.2.3.4 . 4242 dnat ip to numgen inc mod 2 map @t1 meta l4proto tcp dnat ip addr . port to numgen inc mod 2 map @t2 } @@ -72,6 +73,7 @@ table ip6 ip6foo { ip6 saddr dead::2 tcp dport 42 dnat to [c0::1a]:4242 meta l4proto tcp dnat ip6 addr . port to ip6 saddr map @y meta l4proto tcp dnat ip6 addr . port to ip6 saddr . tcp dport map @z + meta l4proto tcp dnat ip6 addr . port to fd00:10:244::4 . 6443 dnat ip6 to numgen inc mod 2 map @t1 meta l4proto tcp dnat ip6 addr . port to numgen inc mod 2 map @t2 } -- 2.55.0