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/* SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-clause) */
/*
* This file contains functions that are used in the packetXX XDP programs to
* manipulate on packets data. The functions are marked as __always_inline, and
* fully defined in this header file to be included in the BPF program.
*/
#ifndef __REWRITE_HELPERS_H
#define __REWRITE_HELPERS_H
#include <linux/bpf.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/if_ether.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
/* Pops the outermost VLAN tag off the packet. Returns the popped VLAN ID on
* success or negative errno on failure.
*/
static __always_inline int vlan_tag_pop(struct xdp_md *ctx, struct ethhdr *eth)
{
void *data_end = (void *)(long)ctx->data_end;
struct ethhdr eth_cpy;
struct vlan_hdr *vlh;
__be16 h_proto;
int vlid;
if (!proto_is_vlan(eth->h_proto))
return -1;
/* Careful with the parenthesis here */
vlh = (void *)(eth + 1);
/* Still need to do bounds checking */
if (vlh + 1 > data_end)
return -1;
/* Save vlan ID for returning, h_proto for updating Ethernet header */
vlid = bpf_ntohs(vlh->h_vlan_TCI);
h_proto = vlh->h_vlan_encapsulated_proto;
/* Make a copy of the outer Ethernet header before we cut it off */
__builtin_memcpy(ð_cpy, eth, sizeof(eth_cpy));
/* Actually adjust the head pointer */
if (bpf_xdp_adjust_head(ctx, (int)sizeof(*vlh)))
return -1;
/* Need to re-evaluate data *and* data_end and do new bounds checking
* after adjusting head
*/
eth = (void *)(long)ctx->data;
data_end = (void *)(long)ctx->data_end;
if (eth + 1 > data_end)
return -1;
/* Copy back the old Ethernet header and update the proto type */
__builtin_memcpy(eth, ð_cpy, sizeof(*eth));
eth->h_proto = h_proto;
return vlid;
}
/* Pushes a new VLAN tag after the Ethernet header. Returns 0 on success,
* -1 on failure.
*/
static __always_inline int vlan_tag_push(struct xdp_md *ctx,
struct ethhdr *eth, int vlid)
{
void *data_end = (void *)(long)ctx->data_end;
struct ethhdr eth_cpy;
struct vlan_hdr *vlh;
/* First copy the original Ethernet header */
__builtin_memcpy(ð_cpy, eth, sizeof(eth_cpy));
/* Then add space in front of the packet */
if (bpf_xdp_adjust_head(ctx, 0 - (int)sizeof(*vlh)))
return -1;
/* Need to re-evaluate data_end and data after head adjustment, and
* bounds check, even though we know there is enough space (as we
* increased it).
*/
data_end = (void *)(long)ctx->data_end;
eth = (void *)(long)ctx->data;
if (eth + 1 > data_end)
return -1;
/* Copy back Ethernet header in the right place, populate VLAN tag with
* ID and proto, and set outer Ethernet header to VLAN type.
*/
__builtin_memcpy(eth, ð_cpy, sizeof(*eth));
vlh = (void *)(eth + 1);
if (vlh + 1 > data_end)
return -1;
vlh->h_vlan_TCI = bpf_htons(vlid);
vlh->h_vlan_encapsulated_proto = eth->h_proto;
eth->h_proto = bpf_htons(ETH_P_8021Q);
return 0;
}
/*
* Swaps destination and source MAC addresses inside an Ethernet header
*/
static __always_inline void swap_src_dst_mac(struct ethhdr *eth)
{
__u8 h_tmp[ETH_ALEN];
__builtin_memcpy(h_tmp, eth->h_source, ETH_ALEN);
__builtin_memcpy(eth->h_source, eth->h_dest, ETH_ALEN);
__builtin_memcpy(eth->h_dest, h_tmp, ETH_ALEN);
}
/*
* Swaps destination and source IPv6 addresses inside an IPv6 header
*/
static __always_inline void swap_src_dst_ipv6(struct ipv6hdr *ipv6)
{
struct in6_addr tmp = ipv6->saddr;
ipv6->saddr = ipv6->daddr;
ipv6->daddr = tmp;
}
/*
* Swaps destination and source IPv4 addresses inside an IPv4 header
*/
static __always_inline void swap_src_dst_ipv4(struct iphdr *iphdr)
{
__be32 tmp = iphdr->saddr;
iphdr->saddr = iphdr->daddr;
iphdr->daddr = tmp;
}
#endif /* __REWRITE_HELPERS_H */
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