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-rw-r--r--contrib/examples/sticky-sockets/sticky-sockets.c337
1 files changed, 337 insertions, 0 deletions
diff --git a/contrib/examples/sticky-sockets/sticky-sockets.c b/contrib/examples/sticky-sockets/sticky-sockets.c
new file mode 100644
index 0000000..1a910b2
--- /dev/null
+++ b/contrib/examples/sticky-sockets/sticky-sockets.c
@@ -0,0 +1,337 @@
+/* Copyright 2017 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, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
+ if (ret < 0)
+ goto err;
+
+ 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, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
+ if (ret < 0)
+ goto err;
+
+ 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;
+}