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/*
* Payload expression and related functions.
*
* Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Development of this code funded by Astaro AG (http://www.astaro.com/)
*/
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <net/if_arp.h>
#include <arpa/inet.h>
#include <linux/netfilter.h>
#include <rule.h>
#include <expression.h>
#include <statement.h>
#include <payload.h>
#include <gmputil.h>
#include <utils.h>
bool payload_is_known(const struct expr *expr)
{
const struct proto_hdr_template *tmpl;
const struct proto_desc *desc;
desc = expr->payload.desc;
tmpl = expr->payload.tmpl;
return desc && tmpl && desc != &proto_unknown &&
tmpl != &proto_unknown_template;
}
static void payload_expr_print(const struct expr *expr, struct output_ctx *octx)
{
const struct proto_desc *desc;
const struct proto_hdr_template *tmpl;
desc = expr->payload.desc;
tmpl = expr->payload.tmpl;
if (payload_is_known(expr))
nft_print(octx, "%s %s", desc->name, tmpl->token);
else
nft_print(octx, "payload @%s,%u,%u",
proto_base_tokens[expr->payload.base],
expr->payload.offset, expr->len);
}
static bool payload_expr_cmp(const struct expr *e1, const struct expr *e2)
{
return e1->payload.desc == e2->payload.desc &&
e1->payload.tmpl == e2->payload.tmpl &&
e1->payload.base == e2->payload.base &&
e1->payload.offset == e2->payload.offset;
}
static void payload_expr_clone(struct expr *new, const struct expr *expr)
{
new->payload.desc = expr->payload.desc;
new->payload.tmpl = expr->payload.tmpl;
new->payload.base = expr->payload.base;
new->payload.offset = expr->payload.offset;
}
/**
* payload_expr_pctx_update - update protocol context based on payload match
*
* @ctx: protocol context
* @expr: relational payload expression
*
* Update protocol context for relational payload expressions.
*/
static void payload_expr_pctx_update(struct proto_ctx *ctx,
const struct expr *expr)
{
const struct expr *left = expr->left, *right = expr->right;
const struct proto_desc *base, *desc;
unsigned int proto = 0;
/* Export the data in the correct byte order */
assert(right->len / BITS_PER_BYTE <= sizeof(proto));
mpz_export_data(constant_data_ptr(proto, right->len), right->value,
right->byteorder, right->len / BITS_PER_BYTE);
base = ctx->protocol[left->payload.base].desc;
desc = proto_find_upper(base, proto);
if (!desc)
return;
assert(desc->base <= PROTO_BASE_MAX);
if (desc->base == base->base) {
assert(base->length > 0);
ctx->protocol[base->base].offset += base->length;
}
proto_ctx_update(ctx, desc->base, &expr->location, desc);
}
static const struct expr_ops payload_expr_ops = {
.type = EXPR_PAYLOAD,
.name = "payload",
.print = payload_expr_print,
.cmp = payload_expr_cmp,
.clone = payload_expr_clone,
.pctx_update = payload_expr_pctx_update,
};
/*
* We normally use 'meta l4proto' to fetch the last l4 header of the
* ipv6 extension header chain so we will also match
* tcp after a fragmentation header, for instance.
* For consistency we also use meta l4proto for ipv4.
*
* If user specifically asks for nexthdr x, don't add another (useless)
* meta dependency.
*/
static bool proto_key_is_protocol(const struct proto_desc *desc, unsigned int type)
{
if (type == desc->protocol_key)
return true;
if (desc == &proto_ip6 && type == IP6HDR_NEXTHDR)
return true;
if (desc == &proto_ip && type == IPHDR_PROTOCOL)
return true;
return false;
}
struct expr *payload_expr_alloc(const struct location *loc,
const struct proto_desc *desc,
unsigned int type)
{
const struct proto_hdr_template *tmpl;
enum proto_bases base;
struct expr *expr;
unsigned int flags = 0;
if (desc != NULL) {
tmpl = &desc->templates[type];
base = desc->base;
if (proto_key_is_protocol(desc, type))
flags = EXPR_F_PROTOCOL;
} else {
tmpl = &proto_unknown_template;
base = PROTO_BASE_INVALID;
desc = &proto_unknown;
}
expr = expr_alloc(loc, &payload_expr_ops, tmpl->dtype,
tmpl->byteorder, tmpl->len);
expr->flags |= flags;
expr->payload.desc = desc;
expr->payload.tmpl = tmpl;
expr->payload.base = base;
expr->payload.offset = tmpl->offset;
return expr;
}
void payload_init_raw(struct expr *expr, enum proto_bases base,
unsigned int offset, unsigned int len)
{
expr->payload.base = base;
expr->payload.offset = offset;
expr->len = len;
}
unsigned int payload_hdr_field(const struct expr *expr)
{
return expr->payload.tmpl - expr->payload.desc->templates;
}
static void payload_stmt_print(const struct stmt *stmt, struct output_ctx *octx)
{
expr_print(stmt->payload.expr, octx);
nft_print(octx, " set ");
expr_print(stmt->payload.val, octx);
}
static const struct stmt_ops payload_stmt_ops = {
.type = STMT_PAYLOAD,
.name = "payload",
.print = payload_stmt_print,
};
struct stmt *payload_stmt_alloc(const struct location *loc,
struct expr *expr, struct expr *val)
{
struct stmt *stmt;
stmt = stmt_alloc(loc, &payload_stmt_ops);
stmt->payload.expr = expr;
stmt->payload.val = val;
return stmt;
}
static int payload_add_dependency(struct eval_ctx *ctx,
const struct proto_desc *desc,
const struct proto_desc *upper,
const struct expr *expr,
struct stmt **res)
{
const struct proto_hdr_template *tmpl;
struct expr *dep, *left, *right;
struct stmt *stmt;
int protocol = proto_find_num(desc, upper);
if (protocol < 0)
return expr_error(ctx->msgs, expr,
"conflicting protocols specified: %s vs. %s",
desc->name, upper->name);
tmpl = &desc->templates[desc->protocol_key];
if (tmpl->meta_key)
left = meta_expr_alloc(&expr->location, tmpl->meta_key);
else
left = payload_expr_alloc(&expr->location, desc, desc->protocol_key);
right = constant_expr_alloc(&expr->location, tmpl->dtype,
tmpl->dtype->byteorder, tmpl->len,
constant_data_ptr(protocol, tmpl->len));
dep = relational_expr_alloc(&expr->location, OP_EQ, left, right);
stmt = expr_stmt_alloc(&dep->location, dep);
if (stmt_evaluate(ctx, stmt) < 0) {
return expr_error(ctx->msgs, expr,
"dependency statement is invalid");
}
relational_expr_pctx_update(&ctx->pctx, dep);
*res = stmt;
return 0;
}
static const struct proto_desc *
payload_get_get_ll_hdr(const struct eval_ctx *ctx)
{
switch (ctx->pctx.family) {
case NFPROTO_INET:
return &proto_inet;
case NFPROTO_BRIDGE:
return &proto_eth;
case NFPROTO_NETDEV:
return &proto_netdev;
default:
break;
}
return NULL;
}
static const struct proto_desc *
payload_gen_special_dependency(struct eval_ctx *ctx, const struct expr *expr)
{
switch (expr->payload.base) {
case PROTO_BASE_LL_HDR:
return payload_get_get_ll_hdr(ctx);
case PROTO_BASE_TRANSPORT_HDR:
if (expr->payload.desc == &proto_icmp ||
expr->payload.desc == &proto_icmp6) {
const struct proto_desc *desc, *desc_upper;
struct stmt *nstmt;
desc = ctx->pctx.protocol[PROTO_BASE_LL_HDR].desc;
if (!desc) {
desc = payload_get_get_ll_hdr(ctx);
if (!desc)
break;
}
desc_upper = &proto_ip6;
if (expr->payload.desc == &proto_icmp)
desc_upper = &proto_ip;
if (payload_add_dependency(ctx, desc, desc_upper,
expr, &nstmt) < 0)
return NULL;
list_add_tail(&nstmt->list, &ctx->stmt->list);
return desc_upper;
}
return &proto_inet_service;
default:
break;
}
return NULL;
}
/**
* payload_gen_dependency - generate match expression on payload dependency
*
* @ctx: evaluation context
* @expr: payload expression
* @res: dependency expression
*
* Generate matches on protocol dependencies. There are two different kinds
* of dependencies:
*
* - A payload expression for a base above the hook base requires a match
* on the protocol value in the lower layer header.
*
* - A payload expression for a base below the hook base is invalid in the
* output path since the lower layer header does not exist when the packet
* is classified. In the input path a payload expressions for a base exactly
* one below the hook base is valid. In this case a match on the device type
* is required to verify that we're dealing with the expected protocol.
*
* Note: since it is unknown to userspace which hooks a chain is called from,
* it is not explicitly verified. The NFT_META_IIFTYPE match will only match
* in the input path though.
*/
int payload_gen_dependency(struct eval_ctx *ctx, const struct expr *expr,
struct stmt **res)
{
const struct hook_proto_desc *h = &hook_proto_desc[ctx->pctx.family];
const struct proto_desc *desc;
struct stmt *stmt;
uint16_t type;
if (expr->payload.base < h->base) {
if (expr->payload.base < h->base - 1)
return expr_error(ctx->msgs, expr,
"payload base is invalid for this "
"family");
if (proto_dev_type(expr->payload.desc, &type) < 0)
return expr_error(ctx->msgs, expr,
"protocol specification is invalid "
"for this family");
stmt = meta_stmt_meta_iiftype(&expr->location, type);
if (stmt_evaluate(ctx, stmt) < 0) {
return expr_error(ctx->msgs, expr,
"dependency statement is invalid");
}
*res = stmt;
return 0;
}
desc = ctx->pctx.protocol[expr->payload.base - 1].desc;
/* Special case for mixed IPv4/IPv6 and bridge tables */
if (desc == NULL)
desc = payload_gen_special_dependency(ctx, expr);
if (desc == NULL)
return expr_error(ctx->msgs, expr,
"ambiguous payload specification: "
"no %s protocol specified",
proto_base_names[expr->payload.base - 1]);
return payload_add_dependency(ctx, desc, expr->payload.desc, expr, res);
}
int exthdr_gen_dependency(struct eval_ctx *ctx, const struct expr *expr,
const struct proto_desc *dependency,
enum proto_bases pb, struct stmt **res)
{
const struct proto_desc *desc;
desc = ctx->pctx.protocol[pb].desc;
if (desc == NULL) {
if (expr->exthdr.op == NFT_EXTHDR_OP_TCPOPT) {
switch (ctx->pctx.family) {
case NFPROTO_NETDEV:
case NFPROTO_BRIDGE:
case NFPROTO_INET:
desc = &proto_inet_service;
goto found;
default:
break;
}
}
return expr_error(ctx->msgs, expr,
"Cannot generate dependency: "
"no %s protocol specified",
proto_base_names[pb]);
}
found:
return payload_add_dependency(ctx, desc, dependency, expr, res);
}
/**
* payload_is_stacked - return whether a payload protocol match defines a stacked
* protocol on the same layer
*
* @desc: current protocol description on this layer
* @expr: payload match
*/
bool payload_is_stacked(const struct proto_desc *desc, const struct expr *expr)
{
const struct proto_desc *next;
if (expr->left->ops->type != EXPR_PAYLOAD ||
!(expr->left->flags & EXPR_F_PROTOCOL) ||
expr->op != OP_EQ)
return false;
next = proto_find_upper(desc, mpz_get_be16(expr->right->value));
return next && next->base == desc->base;
}
void payload_dependency_reset(struct payload_dep_ctx *ctx)
{
memset(ctx, 0, sizeof(*ctx));
}
/**
* payload_dependency_store - store a possibly redundant protocol match
*
* @ctx: payload dependency context
* @stmt: payload match
* @base: base of payload match
*/
void payload_dependency_store(struct payload_dep_ctx *ctx,
struct stmt *stmt, enum proto_bases base)
{
ctx->pbase = base + 1;
ctx->pdep = stmt;
}
/**
* payload_dependency_exists - there is a payload dependency in place
* @ctx: payload dependency context
* @base: payload protocol base
*
* Check if we have seen a protocol key payload expression for this base, we can
* usually remove it if we can infer it from another payload expression in the
* upper base.
*/
bool payload_dependency_exists(const struct payload_dep_ctx *ctx,
enum proto_bases base)
{
return ctx->pbase != PROTO_BASE_INVALID &&
ctx->pbase == base &&
ctx->pdep != NULL;
}
void payload_dependency_release(struct payload_dep_ctx *ctx)
{
list_del(&ctx->pdep->list);
stmt_free(ctx->pdep);
ctx->pbase = PROTO_BASE_INVALID;
if (ctx->pdep == ctx->prev)
ctx->prev = NULL;
ctx->pdep = NULL;
}
static bool payload_may_dependency_kill(struct payload_dep_ctx *ctx,
unsigned int family, struct expr *expr)
{
struct expr *dep = ctx->pdep->expr;
/* Protocol key payload expression at network base such as 'ip6 nexthdr'
* need to be left in place since it implicitly restricts matching to
* IPv6 for the bridge, inet and netdev families.
*/
switch (family) {
case NFPROTO_BRIDGE:
case NFPROTO_NETDEV:
case NFPROTO_INET:
if (dep->left->ops->type == EXPR_PAYLOAD &&
dep->left->payload.base == PROTO_BASE_NETWORK_HDR &&
(dep->left->payload.desc == &proto_ip ||
dep->left->payload.desc == &proto_ip6) &&
expr->payload.base == PROTO_BASE_TRANSPORT_HDR)
return false;
break;
}
return true;
}
/**
* payload_dependency_kill - kill a redundant payload dependency
*
* @ctx: payload dependency context
* @expr: higher layer payload expression
*
* Kill a redundant payload expression if a higher layer payload expression
* implies its existence. Skip this if the dependency is a network payload and
* we are in bridge, netdev and inet families.
*/
void payload_dependency_kill(struct payload_dep_ctx *ctx, struct expr *expr,
unsigned int family)
{
if (payload_dependency_exists(ctx, expr->payload.base) &&
payload_may_dependency_kill(ctx, family, expr))
payload_dependency_release(ctx);
}
void exthdr_dependency_kill(struct payload_dep_ctx *ctx, struct expr *expr,
unsigned int family)
{
switch (expr->exthdr.op) {
case NFT_EXTHDR_OP_TCPOPT:
if (payload_dependency_exists(ctx, PROTO_BASE_TRANSPORT_HDR))
payload_dependency_release(ctx);
break;
case NFT_EXTHDR_OP_IPV6:
if (payload_dependency_exists(ctx, PROTO_BASE_NETWORK_HDR))
payload_dependency_release(ctx);
break;
default:
break;
}
}
/**
* payload_expr_complete - fill in type information of a raw payload expr
*
* @expr: the payload expression
* @ctx: protocol context
*
* Complete the type of a raw payload expression based on the context. If
* insufficient information is available the expression remains unchanged.
*/
void payload_expr_complete(struct expr *expr, const struct proto_ctx *ctx)
{
const struct proto_desc *desc;
const struct proto_hdr_template *tmpl;
unsigned int i;
assert(expr->ops->type == EXPR_PAYLOAD);
desc = ctx->protocol[expr->payload.base].desc;
if (desc == NULL)
return;
assert(desc->base == expr->payload.base);
for (i = 0; i < array_size(desc->templates); i++) {
tmpl = &desc->templates[i];
if (tmpl->offset != expr->payload.offset ||
tmpl->len != expr->len)
continue;
expr->dtype = tmpl->dtype;
expr->payload.desc = desc;
expr->payload.tmpl = tmpl;
return;
}
}
static unsigned int mask_to_offset(const struct expr *mask)
{
return mask ? mpz_scan1(mask->value, 0) : 0;
}
static unsigned int mask_length(const struct expr *mask)
{
unsigned long off;
off = mask_to_offset(mask);
return mpz_scan0(mask->value, off + 1);
}
/**
* payload_expr_trim - trim payload expression according to mask
*
* @expr: the payload expression
* @mask: mask to use when searching templates
* @ctx: protocol context
*
* Walk the template list and determine if a match can be found without
* using the provided mask.
*
* If the mask has to be used, trim the payload expression length accordingly,
* adjust the payload offset and return true to let the caller know that the
* mask can be removed. This function also returns the shift for the right hand
* constant side of the expression.
*/
bool payload_expr_trim(struct expr *expr, struct expr *mask,
const struct proto_ctx *ctx, unsigned int *shift)
{
unsigned int payload_offset = expr->payload.offset;
unsigned int mask_offset = mask_to_offset(mask);
unsigned int mask_len = mask_length(mask);
const struct proto_hdr_template *tmpl;
unsigned int payload_len = expr->len;
const struct proto_desc *desc;
unsigned int off, i, len = 0;
assert(expr->ops->type == EXPR_PAYLOAD);
desc = ctx->protocol[expr->payload.base].desc;
if (desc == NULL)
return false;
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;
}
off = round_up(mask->len, BITS_PER_BYTE) - mask_len;
payload_offset += off;
for (i = 1; i < array_size(desc->templates); i++) {
tmpl = &desc->templates[i];
if (tmpl->offset != payload_offset)
continue;
if (tmpl->len > payload_len)
return false;
payload_len -= tmpl->len;
payload_offset += tmpl->len;
len += tmpl->len;
if (payload_len == 0)
return false;
if (mask_offset + len == mask_len) {
expr->payload.offset += off;
expr->len = len;
*shift = mask_offset;
return true;
}
}
return false;
}
/**
* payload_expr_expand - expand raw merged adjacent payload expressions into its
* original components
*
* @list: list to append expanded payload expressions to
* @expr: the payload expression to expand
* @ctx: protocol context
*
* Expand a merged adjacent payload expression into its original components
* by splitting elements off the beginning matching a payload template.
*
* Note: this requires all payload templates to be specified in ascending
* offset order.
*/
void payload_expr_expand(struct list_head *list, struct expr *expr,
const struct proto_ctx *ctx)
{
const struct proto_hdr_template *tmpl;
const struct proto_desc *desc;
struct expr *new;
unsigned int i;
assert(expr->ops->type == EXPR_PAYLOAD);
desc = ctx->protocol[expr->payload.base].desc;
if (desc == NULL)
goto raw;
assert(desc->base == expr->payload.base);
for (i = 1; i < array_size(desc->templates); i++) {
tmpl = &desc->templates[i];
if (tmpl->offset != expr->payload.offset)
continue;
if (tmpl->len <= expr->len) {
new = payload_expr_alloc(&expr->location, desc, i);
list_add_tail(&new->list, list);
expr->len -= tmpl->len;
expr->payload.offset += tmpl->len;
if (expr->len == 0)
return;
} else
break;
}
raw:
new = payload_expr_alloc(&expr->location, NULL, 0);
payload_init_raw(new, expr->payload.base, expr->payload.offset,
expr->len);
list_add_tail(&new->list, list);
}
static bool payload_is_adjacent(const struct expr *e1, const struct expr *e2)
{
if (e1->payload.base == e2->payload.base &&
e1->payload.offset + e1->len == e2->payload.offset)
return true;
return false;
}
/**
* payload_can_merge - return whether two payload expressions can be merged
*
* @e1: first payload expression
* @e2: second payload expression
*/
bool payload_can_merge(const struct expr *e1, const struct expr *e2)
{
unsigned int total;
if (!payload_is_adjacent(e1, e2))
return false;
if (e1->payload.offset % BITS_PER_BYTE || e1->len % BITS_PER_BYTE ||
e2->payload.offset % BITS_PER_BYTE || e2->len % BITS_PER_BYTE)
return false;
total = e1->len + e2->len;
if (total < e1->len || total > (NFT_REG_SIZE * BITS_PER_BYTE))
return false;
return true;
}
/**
* payload_expr_join - join two adjacent payload expressions
*
* @e1: first payload expression
* @e2: second payload expression
*/
struct expr *payload_expr_join(const struct expr *e1, const struct expr *e2)
{
struct expr *expr;
assert(payload_is_adjacent(e1, e2));
expr = payload_expr_alloc(&internal_location, NULL, 0);
expr->payload.base = e1->payload.base;
expr->payload.offset = e1->payload.offset;
expr->len = e1->len + e2->len;
return expr;
}
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