1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
|
/*
* Copyright (C) 2026 Nick Hainke <vincent@systemli.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 2.1
* as published by the Free Software Foundation
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Bind the sockets of a cgroup to a VRF device, the way 'ip vrf exec' does.
*/
#define _GNU_SOURCE
#include <sys/socket.h>
#include <sys/syscall.h>
#include <linux/bpf.h>
#include <linux/if.h>
#include <linux/if_link.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <errno.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include "../log.h"
#include "vrf.h"
#define BPF_MOV64_IMM(DST, IMM) \
((struct bpf_insn){ .code = BPF_ALU64 | BPF_MOV | BPF_K, .dst_reg = DST, .imm = IMM })
#define BPF_STX_MEM(SIZE, DST, SRC, OFF) \
((struct bpf_insn){ .code = BPF_STX | BPF_SIZE(SIZE) | BPF_MEM, .dst_reg = DST, .src_reg = SRC, .off = OFF })
#define BPF_EXIT_INSN() \
((struct bpf_insn){ .code = BPF_JMP | BPF_EXIT })
static int
vrf_bpf(int cmd, union bpf_attr *attr)
{
return syscall(__NR_bpf, cmd, attr, sizeof(*attr));
}
static bool
vrf_linkinfo_is_vrf(struct rtattr *linkinfo)
{
struct rtattr *rta = RTA_DATA(linkinfo);
int len = RTA_PAYLOAD(linkinfo);
for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len))
if (rta->rta_type == IFLA_INFO_KIND)
return RTA_PAYLOAD(rta) >= strlen("vrf") &&
!strncmp(RTA_DATA(rta), "vrf", RTA_PAYLOAD(rta));
return false;
}
/* returns the ifindex of vrf_name, also checks that it is a VRF device */
static int
vrf_get_ifindex(const char *vrf_name)
{
struct {
struct nlmsghdr hdr;
struct ifinfomsg ifi;
char attrbuf[RTA_SPACE(IFNAMSIZ)];
} req = {
.hdr = {
.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
.nlmsg_type = RTM_GETLINK,
.nlmsg_flags = NLM_F_REQUEST,
.nlmsg_seq = 1,
},
.ifi = { .ifi_family = AF_UNSPEC },
};
size_t namelen = strlen(vrf_name) + 1;
struct nlmsghdr *nh;
struct ifinfomsg *ifi;
struct rtattr *rta;
bool is_vrf = false;
char buf[16384];
int sock, len, ret;
ssize_t n;
if (namelen > IFNAMSIZ)
return -EINVAL;
rta = (struct rtattr *)((char *)&req + NLMSG_ALIGN(req.hdr.nlmsg_len));
rta->rta_type = IFLA_IFNAME;
rta->rta_len = RTA_LENGTH(namelen);
memcpy(RTA_DATA(rta), vrf_name, namelen);
req.hdr.nlmsg_len = NLMSG_ALIGN(req.hdr.nlmsg_len) + RTA_ALIGN(rta->rta_len);
sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
if (sock < 0)
return -errno;
if (send(sock, &req, req.hdr.nlmsg_len, 0) < 0) {
ret = -errno;
close(sock);
return ret;
}
n = recv(sock, buf, sizeof(buf), 0);
ret = -errno;
close(sock);
if (n < 0)
return ret;
nh = (struct nlmsghdr *)buf;
if (!NLMSG_OK(nh, (size_t)n))
return -EIO;
if (nh->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *err = NLMSG_DATA(nh);
if (nh->nlmsg_len < NLMSG_LENGTH(sizeof(*err)) || !err->error)
return -EIO;
return err->error;
}
if (nh->nlmsg_type != RTM_NEWLINK || nh->nlmsg_len < NLMSG_LENGTH(sizeof(*ifi)))
return -EIO;
ifi = NLMSG_DATA(nh);
len = IFLA_PAYLOAD(nh);
for (rta = IFLA_RTA(ifi); RTA_OK(rta, len); rta = RTA_NEXT(rta, len))
if (rta->rta_type == IFLA_LINKINFO)
is_vrf = vrf_linkinfo_is_vrf(rta);
if (!is_vrf) {
ERROR("%s is not a VRF device\n", vrf_name);
return -EINVAL;
}
return ifi->ifi_index;
}
/*
* Attach a program to the cgroup which binds every new AF_INET/AF_INET6
* socket to the VRF. It replaces a program attached earlier.
*/
int
vrf_attach(int cgroup_fd, const char *vrf_name)
{
int ifindex = vrf_get_ifindex(vrf_name);
struct bpf_insn prog[] = {
/* r1 = struct bpf_sock *; r1->bound_dev_if = ifindex */
BPF_MOV64_IMM(BPF_REG_3, ifindex),
BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3,
offsetof(struct bpf_sock, bound_dev_if)),
/* allow */
BPF_MOV64_IMM(BPF_REG_0, 1),
BPF_EXIT_INSN(),
};
union bpf_attr load_attr = {
.prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
.expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE,
.license = (uint64_t)(uintptr_t)"GPL",
.insns = (uint64_t)(uintptr_t)prog,
.insn_cnt = sizeof(prog) / sizeof(prog[0]),
};
union bpf_attr attach_attr = {
.attach_type = BPF_CGROUP_INET_SOCK_CREATE,
.target_fd = cgroup_fd,
};
int prog_fd, ret = 0;
if (ifindex < 0)
return ifindex;
prog_fd = vrf_bpf(BPF_PROG_LOAD, &load_attr);
if (prog_fd < 0)
return -errno;
attach_attr.attach_bpf_fd = prog_fd;
if (vrf_bpf(BPF_PROG_ATTACH, &attach_attr))
ret = -errno;
close(prog_fd);
return ret;
}
void
vrf_detach(int cgroup_fd)
{
union bpf_attr attr = {
.attach_type = BPF_CGROUP_INET_SOCK_CREATE,
.target_fd = cgroup_fd,
};
vrf_bpf(BPF_PROG_DETACH, &attr);
}
|
