wireguard-tools/contrib/sticky-sockets/sticky-sockets.c

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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2015-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*
* This implements userspace semantics of "sticky sockets", modeled after
* WireGuard's kernelspace implementation.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <linux/ipv6.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/udp.h>
#include <arpa/inet.h>
struct magic_endpoint {
union {
struct sockaddr addr;
struct sockaddr_in addr4;
struct sockaddr_in6 addr6;
};
union {
struct {
struct in_addr src4;
int src_if4; /* Essentially the same as addr6->scope_id */
};
struct in6_addr src6;
};
};
ssize_t magic_send4(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
{
ssize_t ret;
struct iovec iovec = {
.iov_base = buffer,
.iov_len = len
};
struct {
struct cmsghdr cmsghdr;
struct in_pktinfo pktinfo;
} cmsg = {
.cmsghdr.cmsg_level = IPPROTO_IP,
.cmsghdr.cmsg_type = IP_PKTINFO,
.cmsghdr.cmsg_len = CMSG_LEN(sizeof(cmsg.pktinfo)),
.pktinfo.ipi_spec_dst = endpoint->src4,
.pktinfo.ipi_ifindex = endpoint->src_if4
};
struct msghdr msghdr = {
.msg_iov = &iovec,
.msg_iovlen = 1,
.msg_name = &endpoint->addr4,
.msg_namelen = sizeof(endpoint->addr4),
.msg_control = &cmsg,
.msg_controllen = sizeof(cmsg)
};
ret = sendmsg(sock, &msghdr, 0);
if (ret < 0 && errno == EINVAL) {
memset(&cmsg.pktinfo, 0, sizeof(cmsg.pktinfo));
endpoint->src4.s_addr = endpoint->src_if4 = 0;
return sendmsg(sock, &msghdr, 0);
}
return ret;
}
ssize_t magic_send6(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
{
ssize_t ret;
struct iovec iovec = {
.iov_base = buffer,
.iov_len = len
};
struct {
struct cmsghdr cmsghdr;
struct in6_pktinfo pktinfo;
} cmsg = {
.cmsghdr.cmsg_level = IPPROTO_IPV6,
.cmsghdr.cmsg_type = IPV6_PKTINFO,
.cmsghdr.cmsg_len = CMSG_LEN(sizeof(cmsg.pktinfo)),
.pktinfo.ipi6_addr = endpoint->src6,
.pktinfo.ipi6_ifindex = memcmp(&in6addr_any, &endpoint->src6, sizeof(endpoint->src6)) ? endpoint->addr6.sin6_scope_id : 0
};
struct msghdr msghdr = {
.msg_iov = &iovec,
.msg_iovlen = 1,
.msg_name = &endpoint->addr6,
.msg_namelen = sizeof(endpoint->addr6),
.msg_control = &cmsg,
.msg_controllen = sizeof(cmsg)
};
ret = sendmsg(sock, &msghdr, 0);
if (ret < 0 && errno == EINVAL) {
memset(&cmsg.pktinfo, 0, sizeof(cmsg.pktinfo));
memset(&endpoint->src6, 0, sizeof(endpoint->src6));
return sendmsg(sock, &msghdr, 0);
}
return ret;
}
ssize_t magic_receive4(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
{
ssize_t ret;
struct iovec iovec = {
.iov_base = buffer,
.iov_len = len
};
struct {
struct cmsghdr cmsghdr;
struct in_pktinfo pktinfo;
} cmsg;
struct msghdr msghdr = {
.msg_iov = &iovec,
.msg_iovlen = 1,
.msg_name = &endpoint->addr4,
.msg_namelen = sizeof(endpoint->addr4),
.msg_control = &cmsg,
.msg_controllen = sizeof(cmsg)
};
ret = recvmsg(sock, &msghdr, 0);
if (ret < 0)
return ret;
if (cmsg.cmsghdr.cmsg_level == IPPROTO_IP && cmsg.cmsghdr.cmsg_type == IP_PKTINFO && cmsg.cmsghdr.cmsg_len >= CMSG_LEN(sizeof(cmsg.pktinfo))) {
endpoint->src4 = cmsg.pktinfo.ipi_spec_dst;
endpoint->src_if4 = cmsg.pktinfo.ipi_ifindex;
}
return ret;
}
ssize_t magic_receive6(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
{
ssize_t ret;
struct iovec iovec = {
.iov_base = buffer,
.iov_len = len
};
struct {
struct cmsghdr cmsghdr;
struct in6_pktinfo pktinfo;
} cmsg;
struct msghdr msghdr = {
.msg_iov = &iovec,
.msg_iovlen = 1,
.msg_name = &endpoint->addr6,
.msg_namelen = sizeof(endpoint->addr6),
.msg_control = &cmsg,
.msg_controllen = sizeof(cmsg)
};
ret = recvmsg(sock, &msghdr, 0);
if (ret < 0)
return ret;
if (cmsg.cmsghdr.cmsg_level == IPPROTO_IPV6 && cmsg.cmsghdr.cmsg_type == IPV6_PKTINFO && cmsg.cmsghdr.cmsg_len >= CMSG_LEN(sizeof(cmsg.pktinfo))) {
endpoint->src6 = cmsg.pktinfo.ipi6_addr;
endpoint->addr6.sin6_scope_id = cmsg.pktinfo.ipi6_ifindex;
}
return ret;
}
void magic_endpoint_clearsrc(struct magic_endpoint *endpoint)
{
if (endpoint->addr.sa_family == AF_INET)
endpoint->src4.s_addr = endpoint->src_if4 = 0;
else if (endpoint->addr.sa_family == AF_INET6)
memset(&endpoint->src6, 0, sizeof(endpoint->src6));
else
memset(endpoint, 0, sizeof(*endpoint));
}
void magic_endpoint_set(struct magic_endpoint *endpoint, const struct sockaddr *addr)
{
if (addr->sa_family == AF_INET)
endpoint->addr4 = *(struct sockaddr_in *)addr;
else if (addr->sa_family == AF_INET6)
endpoint->addr6 = *(struct sockaddr_in6 *)addr;
magic_endpoint_clearsrc(endpoint);
}
int magic_create_sock4(uint16_t listen_port)
{
static const int on = 1;
struct sockaddr_in listen_addr = {
.sin_family = AF_INET,
.sin_port = htons(listen_port),
.sin_addr = INADDR_ANY
};
int fd, ret;
fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0)
return fd;
ret = setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
if (ret < 0)
goto err;
ret = bind(fd, (struct sockaddr *)&listen_addr, sizeof(listen_addr));
if (ret < 0)
goto err;
return fd;
err:
close(fd);
return ret;
}
int magic_create_sock6(uint16_t listen_port)
{
static const int on = 1;
struct sockaddr_in6 listen_addr = {
.sin6_family = AF_INET6,
.sin6_port = htons(listen_port),
.sin6_addr = IN6ADDR_ANY_INIT
};
int fd, ret;
fd = socket(AF_INET6, SOCK_DGRAM, 0);
if (fd < 0)
return fd;
ret = setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on, sizeof(on));
if (ret < 0)
goto err;
ret = setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
if (ret < 0)
goto err;
ret = bind(fd, (struct sockaddr *)&listen_addr, sizeof(listen_addr));
if (ret < 0)
goto err;
return fd;
err:
close(fd);
return ret;
}
int main(int argc, char *argv[])
{
struct magic_endpoint endpoint = { 0 };
int sock;
ssize_t ret;
uint8_t buffer[1024] = { 0 };
char srcaddr[40], dstaddr[40];
if (argc == 2 && !strcmp(argv[1], "-4"))
goto v4;
if (argc == 2 && !strcmp(argv[1], "-6"))
goto v6;
return 1;
v6:
sock = magic_create_sock6(51820);
if (sock < 0) {
perror("magic_create_sock6");
return 1;
}
ret = magic_receive6(sock, &endpoint, buffer, sizeof(buffer));
if (ret < 0) {
perror("magic_receive6");
return 1;
}
if (!inet_ntop(AF_INET6, &endpoint.src6, srcaddr, sizeof(srcaddr))) {
perror("inet_ntop");
return 1;
}
if (!inet_ntop(AF_INET6, &endpoint.addr6.sin6_addr, dstaddr, sizeof(dstaddr))) {
perror("inet_ntop");
return 1;
}
printf("if:%d src:%s dst:%s\n", endpoint.addr6.sin6_scope_id, srcaddr, dstaddr);
printf("Received a packet. Sleeping for 10 seconds before replying, so you have time to mess with your networking setup.\n");
sleep(10);
ret = magic_send6(sock, &endpoint, buffer, sizeof(buffer));
if (ret < 0) {
perror("magic_send6");
return 1;
}
close(sock);
return 0;
v4:
sock = magic_create_sock4(51820);
if (sock < 0) {
perror("magic_create_sock4");
return 1;
}
ret = magic_receive4(sock, &endpoint, buffer, sizeof(buffer));
if (ret < 0) {
perror("magic_receive4");
return 1;
}
if (!inet_ntop(AF_INET, &endpoint.src4, srcaddr, sizeof(srcaddr))) {
perror("inet_ntop");
return 1;
}
if (!inet_ntop(AF_INET, &endpoint.addr4.sin_addr, dstaddr, sizeof(dstaddr))) {
perror("inet_ntop");
return 1;
}
printf("if:%d src:%s dst:%s\n", endpoint.src_if4, srcaddr, dstaddr);
printf("Received a packet. Sleeping for 10 seconds before replying, so you have time to mess with your networking setup.\n");
sleep(10);
ret = magic_send4(sock, &endpoint, buffer, sizeof(buffer));
if (ret < 0) {
perror("magic_send4");
return 1;
}
close(sock);
return 0;
}