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// SPDX-License-Identifier: GPL-2.0
/* In-place tunneling */
#include <stdbool.h>
#include <string.h>
#include <linux/stddef.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <linux/pkt_cls.h>
#include <linux/types.h>
#include "bpf_endian.h"
#include "bpf_helpers.h"
static const int cfg_port = 8000;
struct grev4hdr {
struct iphdr ip;
__be16 flags;
__be16 protocol;
} __attribute__((packed));
struct grev6hdr {
struct ipv6hdr ip;
__be16 flags;
__be16 protocol;
} __attribute__((packed));
static __always_inline void set_ipv4_csum(struct iphdr *iph)
{
__u16 *iph16 = (__u16 *)iph;
__u32 csum;
int i;
iph->check = 0;
#pragma clang loop unroll(full)
for (i = 0, csum = 0; i < sizeof(*iph) >> 1; i++)
csum += *iph16++;
iph->check = ~((csum & 0xffff) + (csum >> 16));
}
static __always_inline int encap_ipv4(struct __sk_buff *skb, bool with_gre)
{
struct grev4hdr h_outer;
struct iphdr iph_inner;
struct tcphdr tcph;
__u64 flags;
int olen;
if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_inner,
sizeof(iph_inner)) < 0)
return TC_ACT_OK;
/* filter only packets we want */
if (iph_inner.ihl != 5 || iph_inner.protocol != IPPROTO_TCP)
return TC_ACT_OK;
if (bpf_skb_load_bytes(skb, ETH_HLEN + sizeof(iph_inner),
&tcph, sizeof(tcph)) < 0)
return TC_ACT_OK;
if (tcph.dest != __bpf_constant_htons(cfg_port))
return TC_ACT_OK;
flags = BPF_F_ADJ_ROOM_FIXED_GSO | BPF_F_ADJ_ROOM_ENCAP_L3_IPV4;
if (with_gre) {
flags |= BPF_F_ADJ_ROOM_ENCAP_L4_GRE;
olen = sizeof(h_outer);
} else {
olen = sizeof(h_outer.ip);
}
/* add room between mac and network header */
if (bpf_skb_adjust_room(skb, olen, BPF_ADJ_ROOM_MAC, flags))
return TC_ACT_SHOT;
/* prepare new outer network header */
h_outer.ip = iph_inner;
h_outer.ip.tot_len = bpf_htons(olen +
bpf_htons(h_outer.ip.tot_len));
if (with_gre) {
h_outer.ip.protocol = IPPROTO_GRE;
h_outer.protocol = bpf_htons(ETH_P_IP);
h_outer.flags = 0;
} else {
h_outer.ip.protocol = IPPROTO_IPIP;
}
set_ipv4_csum((void *)&h_outer.ip);
/* store new outer network header */
if (bpf_skb_store_bytes(skb, ETH_HLEN, &h_outer, olen,
BPF_F_INVALIDATE_HASH) < 0)
return TC_ACT_SHOT;
return TC_ACT_OK;
}
static __always_inline int encap_ipv6(struct __sk_buff *skb, bool with_gre)
{
struct ipv6hdr iph_inner;
struct grev6hdr h_outer;
struct tcphdr tcph;
__u64 flags;
int olen;
if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_inner,
sizeof(iph_inner)) < 0)
return TC_ACT_OK;
/* filter only packets we want */
if (bpf_skb_load_bytes(skb, ETH_HLEN + sizeof(iph_inner),
&tcph, sizeof(tcph)) < 0)
return TC_ACT_OK;
if (tcph.dest != __bpf_constant_htons(cfg_port))
return TC_ACT_OK;
flags = BPF_F_ADJ_ROOM_FIXED_GSO | BPF_F_ADJ_ROOM_ENCAP_L3_IPV6;
if (with_gre) {
flags |= BPF_F_ADJ_ROOM_ENCAP_L4_GRE;
olen = sizeof(h_outer);
} else {
olen = sizeof(h_outer.ip);
}
/* add room between mac and network header */
if (bpf_skb_adjust_room(skb, olen, BPF_ADJ_ROOM_MAC, flags))
return TC_ACT_SHOT;
/* prepare new outer network header */
h_outer.ip = iph_inner;
h_outer.ip.payload_len = bpf_htons(olen +
bpf_ntohs(h_outer.ip.payload_len));
if (with_gre) {
h_outer.ip.nexthdr = IPPROTO_GRE;
h_outer.protocol = bpf_htons(ETH_P_IPV6);
h_outer.flags = 0;
} else {
h_outer.ip.nexthdr = IPPROTO_IPV6;
}
/* store new outer network header */
if (bpf_skb_store_bytes(skb, ETH_HLEN, &h_outer, olen,
BPF_F_INVALIDATE_HASH) < 0)
return TC_ACT_SHOT;
return TC_ACT_OK;
}
SEC("encap_ipip")
int __encap_ipip(struct __sk_buff *skb)
{
if (skb->protocol == __bpf_constant_htons(ETH_P_IP))
return encap_ipv4(skb, false);
else
return TC_ACT_OK;
}
SEC("encap_gre")
int __encap_gre(struct __sk_buff *skb)
{
if (skb->protocol == __bpf_constant_htons(ETH_P_IP))
return encap_ipv4(skb, true);
else
return TC_ACT_OK;
}
SEC("encap_ip6tnl")
int __encap_ip6tnl(struct __sk_buff *skb)
{
if (skb->protocol == __bpf_constant_htons(ETH_P_IPV6))
return encap_ipv6(skb, false);
else
return TC_ACT_OK;
}
SEC("encap_ip6gre")
int __encap_ip6gre(struct __sk_buff *skb)
{
if (skb->protocol == __bpf_constant_htons(ETH_P_IPV6))
return encap_ipv6(skb, true);
else
return TC_ACT_OK;
}
static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
{
char buf[sizeof(struct grev6hdr)];
int olen;
switch (proto) {
case IPPROTO_IPIP:
case IPPROTO_IPV6:
olen = len;
break;
case IPPROTO_GRE:
olen = len + 4 /* gre hdr */;
break;
default:
return TC_ACT_OK;
}
if (bpf_skb_adjust_room(skb, -olen, BPF_ADJ_ROOM_MAC,
BPF_F_ADJ_ROOM_FIXED_GSO))
return TC_ACT_SHOT;
return TC_ACT_OK;
}
static int decap_ipv4(struct __sk_buff *skb)
{
struct iphdr iph_outer;
if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_outer,
sizeof(iph_outer)) < 0)
return TC_ACT_OK;
if (iph_outer.ihl != 5)
return TC_ACT_OK;
return decap_internal(skb, ETH_HLEN, sizeof(iph_outer),
iph_outer.protocol);
}
static int decap_ipv6(struct __sk_buff *skb)
{
struct ipv6hdr iph_outer;
if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_outer,
sizeof(iph_outer)) < 0)
return TC_ACT_OK;
return decap_internal(skb, ETH_HLEN, sizeof(iph_outer),
iph_outer.nexthdr);
}
SEC("decap")
int decap_f(struct __sk_buff *skb)
{
switch (skb->protocol) {
case __bpf_constant_htons(ETH_P_IP):
return decap_ipv4(skb);
case __bpf_constant_htons(ETH_P_IPV6):
return decap_ipv6(skb);
default:
/* does not match, ignore */
return TC_ACT_OK;
}
}
char __license[] SEC("license") = "GPL";
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