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KFunc bpf_ct_set_nat_info

v6.1

Set source or destination network address translation address

Definition

Set source or destination address network translation address of the newly allocated nf_conn before insertion. This must be invoked for referenced PTR_TO_BTF_ID to nf_conn___init.

Parameters

nfct: Pointer to referenced nf_conn object, obtained using bpf_xdp_ct_alloc or bpf_skb_ct_alloc.

addr: Nat source/destination address

port: Nat source/destination port. Non-positive values are interpreted as select a random port.

manip: NF_NAT_MANIP_SRC or NF_NAT_MANIP_DST

int bpf_ct_set_nat_info(struct nf_conn___init *nfct, union nf_inet_addr *addr, int port, nf_nat_manip_type manip)

Usage

The bpf_ct_set_nat_info kfunc helper in order to set source and destination nat addresses/ports in a new allocated connection tracking entry not inserted in the connection tracking table yet.

Program types

The following program types can make use of this kfunc:

Example

// SPDX-License-Identifier: GPL-2.0
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>

#define EAFNOSUPPORT 97
#define EPROTO 71
#define ENONET 64
#define EINVAL 22
#define ENOENT 2

extern unsigned long CONFIG_HZ __kconfig;

int test_einval_bpf_tuple = 0;
int test_einval_reserved = 0;
int test_einval_netns_id = 0;
int test_einval_len_opts = 0;
int test_eproto_l4proto = 0;
int test_enonet_netns_id = 0;
int test_enoent_lookup = 0;
int test_eafnosupport = 0;
int test_alloc_entry = -EINVAL;
int test_insert_entry = -EAFNOSUPPORT;
int test_succ_lookup = -ENOENT;
u32 test_delta_timeout = 0;
u32 test_status = 0;
u32 test_insert_lookup_mark = 0;
int test_snat_addr = -EINVAL;
int test_dnat_addr = -EINVAL;
__be32 saddr = 0;
__be16 sport = 0;
__be32 daddr = 0;
__be16 dport = 0;
int test_exist_lookup = -ENOENT;
u32 test_exist_lookup_mark = 0;

enum nf_nat_manip_type___local {
    NF_NAT_MANIP_SRC___local,
    NF_NAT_MANIP_DST___local
};

struct nf_conn;

struct bpf_ct_opts___local {
    s32 netns_id;
    s32 error;
    u8 l4proto;
    u8 reserved[3];
} __attribute__((preserve_access_index));

struct nf_conn *bpf_xdp_ct_alloc(struct xdp_md *, struct bpf_sock_tuple *, u32,
                 struct bpf_ct_opts___local *, u32) __ksym;
struct nf_conn *bpf_xdp_ct_lookup(struct xdp_md *, struct bpf_sock_tuple *, u32,
                  struct bpf_ct_opts___local *, u32) __ksym;
struct nf_conn *bpf_skb_ct_alloc(struct __sk_buff *, struct bpf_sock_tuple *, u32,
                 struct bpf_ct_opts___local *, u32) __ksym;
struct nf_conn *bpf_skb_ct_lookup(struct __sk_buff *, struct bpf_sock_tuple *, u32,
                  struct bpf_ct_opts___local *, u32) __ksym;
struct nf_conn *bpf_ct_insert_entry(struct nf_conn *) __ksym;
void bpf_ct_release(struct nf_conn *) __ksym;
void bpf_ct_set_timeout(struct nf_conn *, u32) __ksym;
int bpf_ct_change_timeout(struct nf_conn *, u32) __ksym;
int bpf_ct_set_status(struct nf_conn *, u32) __ksym;
int bpf_ct_change_status(struct nf_conn *, u32) __ksym;
int bpf_ct_set_nat_info(struct nf_conn *, union nf_inet_addr *,
            int port, enum nf_nat_manip_type___local) __ksym;

static __always_inline void
nf_ct_test(struct nf_conn *(*lookup_fn)(void *, struct bpf_sock_tuple *, u32,
                    struct bpf_ct_opts___local *, u32),
       struct nf_conn *(*alloc_fn)(void *, struct bpf_sock_tuple *, u32,
                       struct bpf_ct_opts___local *, u32),
       void *ctx)
{
    struct bpf_ct_opts___local opts_def = { .l4proto = IPPROTO_TCP, .netns_id = -1 };
    struct bpf_sock_tuple bpf_tuple;
    struct nf_conn *ct;

    __builtin_memset(&bpf_tuple, 0, sizeof(bpf_tuple.ipv4));

    ct = lookup_fn(ctx, NULL, 0, &opts_def, sizeof(opts_def));
    if (ct)
        bpf_ct_release(ct);
    else
        test_einval_bpf_tuple = opts_def.error;

    opts_def.reserved[0] = 1;
    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
               sizeof(opts_def));
    opts_def.reserved[0] = 0;
    opts_def.l4proto = IPPROTO_TCP;
    if (ct)
        bpf_ct_release(ct);
    else
        test_einval_reserved = opts_def.error;

    opts_def.netns_id = -2;
    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
               sizeof(opts_def));
    opts_def.netns_id = -1;
    if (ct)
        bpf_ct_release(ct);
    else
        test_einval_netns_id = opts_def.error;

    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
               sizeof(opts_def) - 1);
    if (ct)
        bpf_ct_release(ct);
    else
        test_einval_len_opts = opts_def.error;

    opts_def.l4proto = IPPROTO_ICMP;
    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
               sizeof(opts_def));
    opts_def.l4proto = IPPROTO_TCP;
    if (ct)
        bpf_ct_release(ct);
    else
        test_eproto_l4proto = opts_def.error;

    opts_def.netns_id = 0xf00f;
    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
               sizeof(opts_def));
    opts_def.netns_id = -1;
    if (ct)
        bpf_ct_release(ct);
    else
        test_enonet_netns_id = opts_def.error;

    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
               sizeof(opts_def));
    if (ct)
        bpf_ct_release(ct);
    else
        test_enoent_lookup = opts_def.error;

    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4) - 1, &opts_def,
               sizeof(opts_def));
    if (ct)
        bpf_ct_release(ct);
    else
        test_eafnosupport = opts_def.error;

    bpf_tuple.ipv4.saddr = bpf_get_prandom_u32(); /* src IP */
    bpf_tuple.ipv4.daddr = bpf_get_prandom_u32(); /* dst IP */
    bpf_tuple.ipv4.sport = bpf_get_prandom_u32(); /* src port */
    bpf_tuple.ipv4.dport = bpf_get_prandom_u32(); /* dst port */

    ct = alloc_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
              sizeof(opts_def));
    if (ct) {
        __u16 sport = bpf_get_prandom_u32();
        __u16 dport = bpf_get_prandom_u32();
        union nf_inet_addr saddr = {};
        union nf_inet_addr daddr = {};
        struct nf_conn *ct_ins;

        bpf_ct_set_timeout(ct, 10000);
        ct->mark = 77;

        /* snat */
        saddr.ip = bpf_get_prandom_u32();
        bpf_ct_set_nat_info(ct, &saddr, sport, NF_NAT_MANIP_SRC___local);
        /* dnat */
        daddr.ip = bpf_get_prandom_u32();
        bpf_ct_set_nat_info(ct, &daddr, dport, NF_NAT_MANIP_DST___local);

        ct_ins = bpf_ct_insert_entry(ct);
        if (ct_ins) {
            struct nf_conn *ct_lk;

            ct_lk = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4),
                      &opts_def, sizeof(opts_def));
            if (ct_lk) {
                struct nf_conntrack_tuple *tuple;

                /* check snat and dnat addresses */
                tuple = &ct_lk->tuplehash[IP_CT_DIR_REPLY].tuple;
                if (tuple->dst.u3.ip == saddr.ip &&
                    tuple->dst.u.all == bpf_htons(sport))
                    test_snat_addr = 0;
                if (tuple->src.u3.ip == daddr.ip &&
                    tuple->src.u.all == bpf_htons(dport))
                    test_dnat_addr = 0;

                /* update ct entry timeout */
                bpf_ct_change_timeout(ct_lk, 10000);
                test_delta_timeout = ct_lk->timeout - bpf_jiffies64();
                test_delta_timeout /= CONFIG_HZ;
                test_insert_lookup_mark = ct_lk->mark;
                bpf_ct_change_status(ct_lk,
                             IPS_CONFIRMED | IPS_SEEN_REPLY);
                test_status = ct_lk->status;

                bpf_ct_release(ct_lk);
                test_succ_lookup = 0;
            }
            bpf_ct_release(ct_ins);
            test_insert_entry = 0;
        }
        test_alloc_entry = 0;
    }

    bpf_tuple.ipv4.saddr = saddr;
    bpf_tuple.ipv4.daddr = daddr;
    bpf_tuple.ipv4.sport = sport;
    bpf_tuple.ipv4.dport = dport;
    ct = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
               sizeof(opts_def));
    if (ct) {
        test_exist_lookup = 0;
        if (ct->mark == 42) {
            ct->mark++;
            test_exist_lookup_mark = ct->mark;
        }
        bpf_ct_release(ct);
    } else {
        test_exist_lookup = opts_def.error;
    }
}

SEC("xdp")
int nf_xdp_ct_test(struct xdp_md *ctx)
{
    nf_ct_test((void *)bpf_xdp_ct_lookup, (void *)bpf_xdp_ct_alloc, ctx);
    return 0;
}

SEC("tc")
int nf_skb_ct_test(struct __sk_buff *ctx)
{
    nf_ct_test((void *)bpf_skb_ct_lookup, (void *)bpf_skb_ct_alloc, ctx);
    return 0;
}

char _license[] SEC("license") = "GPL";