From 72f0ca53bcc6586b921ff70dac9f3a911e4ec170 Mon Sep 17 00:00:00 2001

From: Phil Sutter <psutter@redhat.com>

Date: Thu, 9 Feb 2023 10:27:57 +0100

Subject: [PATCH] proto: track full stack of seen l2 protocols, not just

 cumulative offset

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2094887

Upstream Status: nftables commit 0d9daa0407212

commit 0d9daa0407212c8cc89b3ea8aee031ddf0109b08

Author: Florian Westphal <fw@strlen.de>

Date:   Mon Jul 25 14:32:13 2022 +0200

    proto: track full stack of seen l2 protocols, not just cumulative offset

    For input, a cumulative size counter of all pushed l2 headers is enough,

    because we have the full expression tree available to us.

    For delinearization we need to track all seen l2 headers, else we lose

    information that we might need at a later time.

    Consider:

    rule netdev nt nc set update ether saddr . vlan id

    during delinearization, the vlan proto_desc replaces the ethernet one,

    and by the time we try to split the concatenation apart we will search

    the ether saddr offset vs. the templates for proto_vlan.

    This replaces the offset with an array that stores the protocol

    descriptions seen.

    Then, if the payload offset is larger than our description, search the

    l2 stack and adjust the offset until we're within the expected offset

    boundary.

    Reported-by: Eric Garver <eric@garver.life>

    Signed-off-by: Florian Westphal <fw@strlen.de>

Signed-off-by: Phil Sutter <psutter@redhat.com>

---

 include/proto.h           |  3 +-

 src/evaluate.c            | 15 +++++++--

 src/netlink_delinearize.c |  5 ---

 src/payload.c             | 67 ++++++++++++++++++++++++++++++++-------

 src/proto.c               |  2 --

 5 files changed, 71 insertions(+), 21 deletions(-)

diff --git a/include/proto.h b/include/proto.h

index a04240a..35e760c 100644

--- a/include/proto.h

+++ b/include/proto.h

@@ -193,13 +193,14 @@ struct proto_ctx {

 	struct {

 		struct location			location;

 		const struct proto_desc		*desc;

-		unsigned int			offset;

 		struct {

 			struct location		location;

 			const struct proto_desc	*desc;

 		} protos[PROTO_CTX_NUM_PROTOS];

 		unsigned int			num_protos;

 	} protocol[PROTO_BASE_MAX + 1];

+	const struct proto_desc *stacked_ll[PROTO_CTX_NUM_PROTOS];

+	uint8_t stacked_ll_count;

 };

 extern void proto_ctx_init(struct proto_ctx *ctx, unsigned int family,

diff --git a/src/evaluate.c b/src/evaluate.c

index 82bf131..9246064 100644

--- a/src/evaluate.c

+++ b/src/evaluate.c

@@ -678,7 +678,13 @@ static int resolve_protocol_conflict(struct eval_ctx *ctx,

 	    conflict_resolution_gen_dependency(ctx, link, payload, &nstmt) < 0)

 		return 1;

-	payload->payload.offset += ctx->pctx.protocol[base].offset;

+	if (base == PROTO_BASE_LL_HDR) {

+		unsigned int i;

+

+		for (i = 0; i < ctx->pctx.stacked_ll_count; i++)

+			payload->payload.offset += ctx->pctx.stacked_ll[i]->length;

+	}

+

 	rule_stmt_insert_at(ctx->rule, nstmt, ctx->stmt);

 	return 0;

@@ -727,7 +733,12 @@ static int __expr_evaluate_payload(struct eval_ctx *ctx, struct expr *expr)

 	if (desc == payload->payload.desc) {

 		const struct proto_hdr_template *tmpl;

-		payload->payload.offset += ctx->pctx.protocol[base].offset;

+		if (desc->base == PROTO_BASE_LL_HDR) {

+			unsigned int i;

+

+			for (i = 0; i < ctx->pctx.stacked_ll_count; i++)

+				payload->payload.offset += ctx->pctx.stacked_ll[i]->length;

+		}

 check_icmp:

 		if (desc != &proto_icmp && desc != &proto_icmp6)

 			return 0;

diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c

index cba419d..0b5519d 100644

--- a/src/netlink_delinearize.c

+++ b/src/netlink_delinearize.c

@@ -1976,11 +1976,6 @@ static void payload_match_postprocess(struct rule_pp_ctx *ctx,

 				      struct expr *expr,

 				      struct expr *payload)

 {

-	enum proto_bases base = payload->payload.base;

-

-	assert(payload->payload.offset >= ctx->pctx.protocol[base].offset);

-	payload->payload.offset -= ctx->pctx.protocol[base].offset;

-

 	switch (expr->op) {

 	case OP_EQ:

 	case OP_NEQ:

diff --git a/src/payload.c b/src/payload.c

index 66418cd..2c0d0ac 100644

--- a/src/payload.c

+++ b/src/payload.c

@@ -116,8 +116,13 @@ static void payload_expr_pctx_update(struct proto_ctx *ctx,

 	if (desc->base == base->base) {

 		assert(base->length > 0);

-		if (!left->payload.is_raw)

-			ctx->protocol[base->base].offset += base->length;

+		if (!left->payload.is_raw) {

+			if (desc->base == PROTO_BASE_LL_HDR &&

+			    ctx->stacked_ll_count < PROTO_CTX_NUM_PROTOS) {

+				ctx->stacked_ll[ctx->stacked_ll_count] = base;

+				ctx->stacked_ll_count++;

+			}

+		}

 	}

 	proto_ctx_update(ctx, desc->base, loc, desc);

 }

@@ -869,6 +874,38 @@ void exthdr_dependency_kill(struct payload_dep_ctx *ctx, struct expr *expr,

 	}

 }

+static const struct proto_desc *get_stacked_desc(const struct proto_ctx *ctx,

+						 const struct proto_desc *top,

+						 const struct expr *e,

+						 unsigned int *skip)

+{

+	unsigned int i, total, payload_offset = e->payload.offset;

+

+	assert(e->etype == EXPR_PAYLOAD);

+

+	if (e->payload.base != PROTO_BASE_LL_HDR ||

+	    payload_offset < top->length) {

+		*skip = 0;

+		return top;

+	}

+

+	for (i = 0, total = 0; i < ctx->stacked_ll_count; i++) {

+		const struct proto_desc *stacked;

+

+		stacked = ctx->stacked_ll[i];

+		if (payload_offset < stacked->length) {

+			*skip = total;

+			return stacked;

+		}

+

+		payload_offset -= stacked->length;

+		total += stacked->length;

+	}

+

+	*skip = total;

+	return top;

+}

+

 /**

  * payload_expr_complete - fill in type information of a raw payload expr

  *

@@ -880,9 +917,10 @@ void exthdr_dependency_kill(struct payload_dep_ctx *ctx, struct expr *expr,

  */

 void payload_expr_complete(struct expr *expr, const struct proto_ctx *ctx)

 {

+	unsigned int payload_offset = expr->payload.offset;

 	const struct proto_desc *desc;

 	const struct proto_hdr_template *tmpl;

-	unsigned int i;

+	unsigned int i, total;

 	assert(expr->etype == EXPR_PAYLOAD);

@@ -891,9 +929,12 @@ void payload_expr_complete(struct expr *expr, const struct proto_ctx *ctx)

 		return;

 	assert(desc->base == expr->payload.base);

+	desc = get_stacked_desc(ctx, desc, expr, &total);

+	payload_offset -= total;

+

 	for (i = 0; i < array_size(desc->templates); i++) {

 		tmpl = &desc->templates[i];

-		if (tmpl->offset != expr->payload.offset ||

+		if (tmpl->offset != payload_offset ||

 		    tmpl->len    != expr->len)

 			continue;

@@ -950,6 +991,7 @@ bool payload_expr_trim(struct expr *expr, struct expr *mask,

 	unsigned int payload_len = expr->len;

 	const struct proto_desc *desc;

 	unsigned int off, i, len = 0;

+	unsigned int total;

 	assert(expr->etype == EXPR_PAYLOAD);

@@ -959,10 +1001,8 @@ bool payload_expr_trim(struct expr *expr, struct expr *mask,

 	assert(desc->base == expr->payload.base);

-	if (ctx->protocol[expr->payload.base].offset) {

-		assert(payload_offset >= ctx->protocol[expr->payload.base].offset);

-		payload_offset -= ctx->protocol[expr->payload.base].offset;

-	}

+	desc = get_stacked_desc(ctx, desc, expr, &total);

+	payload_offset -= total;

 	off = round_up(mask->len, BITS_PER_BYTE) - mask_len;

 	payload_offset += off;

@@ -1009,10 +1049,11 @@ bool payload_expr_trim(struct expr *expr, struct expr *mask,

 void payload_expr_expand(struct list_head *list, struct expr *expr,

 			 const struct proto_ctx *ctx)

 {

+	unsigned int payload_offset = expr->payload.offset;

 	const struct proto_hdr_template *tmpl;

 	const struct proto_desc *desc;

+	unsigned int i, total;

 	struct expr *new;

-	unsigned int i;

 	assert(expr->etype == EXPR_PAYLOAD);

@@ -1021,13 +1062,16 @@ void payload_expr_expand(struct list_head *list, struct expr *expr,

 		goto raw;

 	assert(desc->base == expr->payload.base);

+	desc = get_stacked_desc(ctx, desc, expr, &total);

+	payload_offset -= total;

+

 	for (i = 1; i < array_size(desc->templates); i++) {

 		tmpl = &desc->templates[i];

 		if (tmpl->len == 0)

 			break;

-		if (tmpl->offset != expr->payload.offset)

+		if (tmpl->offset != payload_offset)

 			continue;

 		if (tmpl->icmp_dep && ctx->th_dep.icmp.type &&

@@ -1039,6 +1083,7 @@ void payload_expr_expand(struct list_head *list, struct expr *expr,

 			list_add_tail(&new->list, list);

 			expr->len	     -= tmpl->len;

 			expr->payload.offset += tmpl->len;

+			payload_offset       += tmpl->len;

 			if (expr->len == 0)

 				return;

 		} else if (expr->len > 0) {

@@ -1051,7 +1096,7 @@ void payload_expr_expand(struct list_head *list, struct expr *expr,

 	}

 raw:

 	new = payload_expr_alloc(&expr->location, NULL, 0);

-	payload_init_raw(new, expr->payload.base, expr->payload.offset,

+	payload_init_raw(new, expr->payload.base, payload_offset,

 			 expr->len);

 	list_add_tail(&new->list, list);

 }

diff --git a/src/proto.c b/src/proto.c

index a013a00..2663f21 100644

--- a/src/proto.c

+++ b/src/proto.c

@@ -160,8 +160,6 @@ static void proto_ctx_debug(const struct proto_ctx *ctx, enum proto_bases base,

 			 proto_base_names[i],

 			 ctx->protocol[i].desc ? ctx->protocol[i].desc->name :

 						 "none");

-		if (ctx->protocol[i].offset)

-			pr_debug(" (offset: %u)", ctx->protocol[i].offset);

 		if (i == base)

 			pr_debug(" <-");

 		pr_debug("\n");

-- 

2.39.1