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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2018 Facebook
#include <linux/stddef.h>
#include <linux/bpf.h>
#include <sys/socket.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include <bpf_sockopt_helpers.h>
#define SRC_REWRITE_IP6_0 0
#define SRC_REWRITE_IP6_1 0
#define SRC_REWRITE_IP6_2 0
#define SRC_REWRITE_IP6_3 6
#define DST_REWRITE_IP6_0 0
#define DST_REWRITE_IP6_1 0
#define DST_REWRITE_IP6_2 0
#define DST_REWRITE_IP6_3 1
#define DST_REWRITE_IP6_V4_MAPPED_0 0
#define DST_REWRITE_IP6_V4_MAPPED_1 0
#define DST_REWRITE_IP6_V4_MAPPED_2 0x0000FFFF
#define DST_REWRITE_IP6_V4_MAPPED_3 0xc0a80004 // 192.168.0.4
#define DST_REWRITE_PORT6 6666
SEC("cgroup/sendmsg6")
int sendmsg_v6_prog(struct bpf_sock_addr *ctx)
{
if (ctx->type != SOCK_DGRAM)
return 0;
if (!get_set_sk_priority(ctx))
return 0;
/* Rewrite source. */
if (ctx->msg_src_ip6[3] == bpf_htonl(1) ||
ctx->msg_src_ip6[3] == bpf_htonl(0)) {
ctx->msg_src_ip6[0] = bpf_htonl(SRC_REWRITE_IP6_0);
ctx->msg_src_ip6[1] = bpf_htonl(SRC_REWRITE_IP6_1);
ctx->msg_src_ip6[2] = bpf_htonl(SRC_REWRITE_IP6_2);
ctx->msg_src_ip6[3] = bpf_htonl(SRC_REWRITE_IP6_3);
} else {
/* Unexpected source. Reject sendmsg. */
return 0;
}
/* Rewrite destination. */
if (ctx->user_ip6[0] == bpf_htonl(0xFACEB00C)) {
ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_0);
ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_1);
ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2);
ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_3);
ctx->user_port = bpf_htons(DST_REWRITE_PORT6);
} else {
/* Unexpected destination. Reject sendmsg. */
return 0;
}
return 1;
}
SEC("cgroup/sendmsg6")
int sendmsg_v6_v4mapped_prog(struct bpf_sock_addr *ctx)
{
/* Rewrite source. */
ctx->msg_src_ip6[0] = bpf_htonl(SRC_REWRITE_IP6_0);
ctx->msg_src_ip6[1] = bpf_htonl(SRC_REWRITE_IP6_1);
ctx->msg_src_ip6[2] = bpf_htonl(SRC_REWRITE_IP6_2);
ctx->msg_src_ip6[3] = bpf_htonl(SRC_REWRITE_IP6_3);
/* Rewrite destination. */
ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_V4_MAPPED_0);
ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_V4_MAPPED_1);
ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_V4_MAPPED_2);
ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_V4_MAPPED_3);
ctx->user_port = bpf_htons(DST_REWRITE_PORT6);
return 1;
}
SEC("cgroup/sendmsg6")
int sendmsg_v6_wildcard_prog(struct bpf_sock_addr *ctx)
{
/* Rewrite source. */
ctx->msg_src_ip6[0] = bpf_htonl(SRC_REWRITE_IP6_0);
ctx->msg_src_ip6[1] = bpf_htonl(SRC_REWRITE_IP6_1);
ctx->msg_src_ip6[2] = bpf_htonl(SRC_REWRITE_IP6_2);
ctx->msg_src_ip6[3] = bpf_htonl(SRC_REWRITE_IP6_3);
/* Rewrite destination. */
ctx->user_ip6[0] = bpf_htonl(0);
ctx->user_ip6[1] = bpf_htonl(0);
ctx->user_ip6[2] = bpf_htonl(0);
ctx->user_ip6[3] = bpf_htonl(0);
ctx->user_port = bpf_htons(DST_REWRITE_PORT6);
return 1;
}
SEC("cgroup/sendmsg6")
int sendmsg_v6_preserve_dst_prog(struct bpf_sock_addr *ctx)
{
return 1;
}
SEC("cgroup/sendmsg6")
int sendmsg_v6_deny_prog(struct bpf_sock_addr *ctx)
{
return 0;
}
char _license[] SEC("license") = "GPL";
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