contrib: add sticky sockets example code
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld
parent
92feabdd17
commit
6c7d67acfe
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Sticky Sockets
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==============
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This is a small userspace mini-library that implements as close to
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possible how the kernel does its sticky src address sending.
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Binary file not shown.
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/* Copyright 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*
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* This implements userspace semantics of "sticky sockets", modeled after
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* WireGuard's kernelspace implementation.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include <linux/ipv6.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netinet/udp.h>
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#include <arpa/inet.h>
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struct magic_endpoint {
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union {
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struct sockaddr addr;
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struct sockaddr_in addr4;
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struct sockaddr_in6 addr6;
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};
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union {
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struct {
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struct in_addr src4;
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int src_if4; /* Essentially the same as addr6->scope_id */
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};
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struct in6_addr src6;
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};
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};
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ssize_t magic_send4(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
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{
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ssize_t ret;
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struct iovec iovec = {
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.iov_base = buffer,
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.iov_len = len
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};
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struct {
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struct cmsghdr cmsghdr;
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struct in_pktinfo pktinfo;
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} cmsg = {
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.cmsghdr.cmsg_level = IPPROTO_IP,
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.cmsghdr.cmsg_type = IP_PKTINFO,
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.cmsghdr.cmsg_len = CMSG_LEN(sizeof(cmsg.pktinfo)),
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.pktinfo.ipi_spec_dst = endpoint->src4,
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.pktinfo.ipi_ifindex = endpoint->src_if4
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};
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struct msghdr msghdr = {
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.msg_iov = &iovec,
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.msg_iovlen = 1,
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.msg_name = &endpoint->addr4,
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.msg_namelen = sizeof(endpoint->addr4),
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.msg_control = &cmsg,
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.msg_controllen = sizeof(cmsg)
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};
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ret = sendmsg(sock, &msghdr, 0);
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if (ret < 0 && errno == EINVAL) {
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memset(&cmsg.pktinfo, 0, sizeof(cmsg.pktinfo));
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endpoint->src4.s_addr = endpoint->src_if4 = 0;
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return sendmsg(sock, &msghdr, 0);
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}
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return ret;
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}
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ssize_t magic_send6(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
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{
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ssize_t ret;
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struct iovec iovec = {
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.iov_base = buffer,
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.iov_len = len
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};
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struct {
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struct cmsghdr cmsghdr;
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struct in6_pktinfo pktinfo;
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} cmsg = {
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.cmsghdr.cmsg_level = IPPROTO_IPV6,
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.cmsghdr.cmsg_type = IPV6_PKTINFO,
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.cmsghdr.cmsg_len = CMSG_LEN(sizeof(cmsg.pktinfo)),
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.pktinfo.ipi6_addr = endpoint->src6,
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.pktinfo.ipi6_ifindex = memcmp(&in6addr_any, &endpoint->src6, sizeof(endpoint->src6)) ? endpoint->addr6.sin6_scope_id : 0
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};
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struct msghdr msghdr = {
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.msg_iov = &iovec,
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.msg_iovlen = 1,
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.msg_name = &endpoint->addr6,
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.msg_namelen = sizeof(endpoint->addr6),
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.msg_control = &cmsg,
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.msg_controllen = sizeof(cmsg)
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};
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ret = sendmsg(sock, &msghdr, 0);
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if (ret < 0 && errno == EINVAL) {
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memset(&cmsg.pktinfo, 0, sizeof(cmsg.pktinfo));
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memset(&endpoint->src6, 0, sizeof(endpoint->src6));
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return sendmsg(sock, &msghdr, 0);
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}
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return ret;
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}
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ssize_t magic_receive4(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
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{
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ssize_t ret;
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struct iovec iovec = {
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.iov_base = buffer,
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.iov_len = len
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};
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struct {
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struct cmsghdr cmsghdr;
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struct in_pktinfo pktinfo;
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} cmsg;
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struct msghdr msghdr = {
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.msg_iov = &iovec,
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.msg_iovlen = 1,
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.msg_name = &endpoint->addr4,
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.msg_namelen = sizeof(endpoint->addr4),
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.msg_control = &cmsg,
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.msg_controllen = sizeof(cmsg)
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};
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ret = recvmsg(sock, &msghdr, 0);
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if (ret < 0)
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return ret;
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if (cmsg.cmsghdr.cmsg_level == IPPROTO_IP && cmsg.cmsghdr.cmsg_type == IP_PKTINFO && cmsg.cmsghdr.cmsg_len >= CMSG_LEN(sizeof(cmsg.pktinfo))) {
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endpoint->src4 = cmsg.pktinfo.ipi_spec_dst;
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endpoint->src_if4 = cmsg.pktinfo.ipi_ifindex;
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}
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return ret;
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}
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ssize_t magic_receive6(int sock, struct magic_endpoint *endpoint, void *buffer, size_t len)
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{
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ssize_t ret;
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struct iovec iovec = {
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.iov_base = buffer,
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.iov_len = len
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};
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struct {
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struct cmsghdr cmsghdr;
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struct in6_pktinfo pktinfo;
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} cmsg;
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struct msghdr msghdr = {
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.msg_iov = &iovec,
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.msg_iovlen = 1,
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.msg_name = &endpoint->addr6,
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.msg_namelen = sizeof(endpoint->addr6),
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.msg_control = &cmsg,
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.msg_controllen = sizeof(cmsg)
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};
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ret = recvmsg(sock, &msghdr, 0);
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if (ret < 0)
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return ret;
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if (cmsg.cmsghdr.cmsg_level == IPPROTO_IPV6 && cmsg.cmsghdr.cmsg_type == IPV6_PKTINFO && cmsg.cmsghdr.cmsg_len >= CMSG_LEN(sizeof(cmsg.pktinfo))) {
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endpoint->src6 = cmsg.pktinfo.ipi6_addr;
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endpoint->addr6.sin6_scope_id = cmsg.pktinfo.ipi6_ifindex;
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}
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return ret;
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}
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void magic_endpoint_clearsrc(struct magic_endpoint *endpoint)
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{
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if (endpoint->addr.sa_family == AF_INET)
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endpoint->src4.s_addr = endpoint->src_if4 = 0;
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else if (endpoint->addr.sa_family == AF_INET6)
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memset(&endpoint->src6, 0, sizeof(endpoint->src6));
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else
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memset(endpoint, 0, sizeof(*endpoint));
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}
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void magic_endpoint_set(struct magic_endpoint *endpoint, const struct sockaddr *addr)
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{
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if (addr->sa_family == AF_INET)
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endpoint->addr4 = *(struct sockaddr_in *)addr;
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else if (addr->sa_family == AF_INET6)
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endpoint->addr6 = *(struct sockaddr_in6 *)addr;
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magic_endpoint_clearsrc(endpoint);
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}
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int magic_create_sock4(uint16_t listen_port)
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{
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static const int on = 1;
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struct sockaddr_in listen_addr = {
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.sin_family = AF_INET,
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.sin_port = htons(listen_port),
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.sin_addr = INADDR_ANY
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};
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int fd, ret;
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fd = socket(AF_INET, SOCK_DGRAM, 0);
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if (fd < 0)
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return fd;
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ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
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if (ret < 0)
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goto err;
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ret = setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
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if (ret < 0)
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goto err;
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ret = bind(fd, (struct sockaddr *)&listen_addr, sizeof(listen_addr));
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if (ret < 0)
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goto err;
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return fd;
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err:
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close(fd);
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return ret;
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}
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int magic_create_sock6(uint16_t listen_port)
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{
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static const int on = 1;
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struct sockaddr_in6 listen_addr = {
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.sin6_family = AF_INET6,
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.sin6_port = htons(listen_port),
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.sin6_addr = IN6ADDR_ANY_INIT
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};
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int fd, ret;
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fd = socket(AF_INET6, SOCK_DGRAM, 0);
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if (fd < 0)
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return fd;
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ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
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if (ret < 0)
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goto err;
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ret = setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on, sizeof(on));
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if (ret < 0)
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goto err;
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ret = setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
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if (ret < 0)
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goto err;
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ret = bind(fd, (struct sockaddr *)&listen_addr, sizeof(listen_addr));
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if (ret < 0)
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goto err;
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return fd;
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err:
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close(fd);
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return ret;
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}
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int main(int argc, char *argv[])
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{
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struct magic_endpoint endpoint = { 0 };
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int sock;
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ssize_t ret;
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uint8_t buffer[1024] = { 0 };
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char srcaddr[40], dstaddr[40];
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if (argc == 2 && !strcmp(argv[1], "-4"))
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goto v4;
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if (argc == 2 && !strcmp(argv[1], "-6"))
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goto v6;
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return 1;
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v6:
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sock = magic_create_sock6(51820);
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if (sock < 0) {
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perror("magic_create_sock6");
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return 1;
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}
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ret = magic_receive6(sock, &endpoint, buffer, sizeof(buffer));
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if (ret < 0) {
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perror("magic_receive6");
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return 1;
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}
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if (!inet_ntop(AF_INET6, &endpoint.src6, srcaddr, sizeof(srcaddr))) {
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perror("inet_ntop");
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return 1;
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}
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if (!inet_ntop(AF_INET6, &endpoint.addr6.sin6_addr, dstaddr, sizeof(dstaddr))) {
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perror("inet_ntop");
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return 1;
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}
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printf("if:%d src:%s dst:%s\n", endpoint.addr6.sin6_scope_id, srcaddr, dstaddr);
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printf("Received a packet. Sleeping for 10 seconds before replying, so you have time to mess with your networking setup.\n");
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sleep(10);
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ret = magic_send6(sock, &endpoint, buffer, sizeof(buffer));
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if (ret < 0) {
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perror("magic_send6");
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return 1;
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}
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close(sock);
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return 0;
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v4:
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sock = magic_create_sock4(51820);
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if (sock < 0) {
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perror("magic_create_sock4");
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return 1;
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}
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ret = magic_receive4(sock, &endpoint, buffer, sizeof(buffer));
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if (ret < 0) {
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perror("magic_receive4");
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return 1;
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}
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if (!inet_ntop(AF_INET, &endpoint.src4, srcaddr, sizeof(srcaddr))) {
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perror("inet_ntop");
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return 1;
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}
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if (!inet_ntop(AF_INET, &endpoint.addr4.sin_addr, dstaddr, sizeof(dstaddr))) {
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perror("inet_ntop");
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return 1;
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}
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printf("if:%d src:%s dst:%s\n", endpoint.src_if4, srcaddr, dstaddr);
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printf("Received a packet. Sleeping for 10 seconds before replying, so you have time to mess with your networking setup.\n");
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sleep(10);
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ret = magic_send4(sock, &endpoint, buffer, sizeof(buffer));
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if (ret < 0) {
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perror("magic_send4");
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return 1;
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}
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close(sock);
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return 0;
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}
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