1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright 2018 Google Inc.
4 * Author: Soheil Hassas Yeganeh (soheil@google.com)
6 * Simple example on how to use TCP_INQ and TCP_CM_INQ.
11 #include <netinet/in.h>
12 #include <netinet/tcp.h>
18 #include <sys/socket.h>
26 #define TCP_CM_INQ TCP_INQ
32 static int family = AF_INET6;
33 static socklen_t addr_len = sizeof(struct sockaddr_in6);
34 static int port = 4974;
36 static void setup_loopback_addr(int family, struct sockaddr_storage *sockaddr)
38 struct sockaddr_in6 *addr6 = (void *) sockaddr;
39 struct sockaddr_in *addr4 = (void *) sockaddr;
43 memset(addr4, 0, sizeof(*addr4));
44 addr4->sin_family = AF_INET;
45 addr4->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
46 addr4->sin_port = htons(port);
49 memset(addr6, 0, sizeof(*addr6));
50 addr6->sin6_family = AF_INET6;
51 addr6->sin6_addr = in6addr_loopback;
52 addr6->sin6_port = htons(port);
55 error(1, 0, "illegal family");
59 void *start_server(void *arg)
61 int server_fd = (int)(unsigned long)arg;
62 struct sockaddr_in addr;
63 socklen_t addrlen = sizeof(addr);
68 buf = malloc(BUF_SIZE);
71 fd = accept(server_fd, (struct sockaddr *)&addr, &addrlen);
77 r = send(fd, buf, BUF_SIZE, 0);
78 } while (r < 0 && errno == EINTR);
82 fprintf(stderr, "can only send %d bytes\n", r);
83 /* TCP_INQ can overestimate in-queue by one byte if we send
84 * the FIN packet. Sleep for 1 second, so that the client
85 * likely invoked recvmsg().
96 int main(int argc, char *argv[])
98 struct sockaddr_storage listen_addr, addr;
99 int c, one = 1, inq = -1;
100 pthread_t server_thread;
101 char cmsgbuf[CMSG_SIZE];
108 while ((c = getopt(argc, argv, "46p:")) != -1) {
112 addr_len = sizeof(struct sockaddr_in);
116 addr_len = sizeof(struct sockaddr_in6);
124 server_fd = socket(family, SOCK_STREAM, 0);
126 error(1, errno, "server socket");
127 setup_loopback_addr(family, &listen_addr);
128 if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR,
129 &one, sizeof(one)) != 0)
130 error(1, errno, "setsockopt(SO_REUSEADDR)");
131 if (bind(server_fd, (const struct sockaddr *)&listen_addr,
133 error(1, errno, "bind");
134 if (listen(server_fd, 128) == -1)
135 error(1, errno, "listen");
136 if (pthread_create(&server_thread, NULL, start_server,
137 (void *)(unsigned long)server_fd) != 0)
138 error(1, errno, "pthread_create");
140 fd = socket(family, SOCK_STREAM, 0);
142 error(1, errno, "client socket");
143 setup_loopback_addr(family, &addr);
144 if (connect(fd, (const struct sockaddr *)&addr, addr_len) == -1)
145 error(1, errno, "connect");
146 if (setsockopt(fd, SOL_TCP, TCP_INQ, &one, sizeof(one)) != 0)
147 error(1, errno, "setsockopt(TCP_INQ)");
153 msg.msg_control = cmsgbuf;
154 msg.msg_controllen = sizeof(cmsgbuf);
157 buf = malloc(BUF_SIZE);
158 iov[0].iov_base = buf;
159 iov[0].iov_len = BUF_SIZE / 2;
161 if (recvmsg(fd, &msg, 0) != iov[0].iov_len)
162 error(1, errno, "recvmsg");
163 if (msg.msg_flags & MSG_CTRUNC)
164 error(1, 0, "control message is truncated");
166 for (cm = CMSG_FIRSTHDR(&msg); cm; cm = CMSG_NXTHDR(&msg, cm))
167 if (cm->cmsg_level == SOL_TCP && cm->cmsg_type == TCP_CM_INQ)
168 inq = *((int *) CMSG_DATA(cm));
170 if (inq != BUF_SIZE - iov[0].iov_len) {
171 fprintf(stderr, "unexpected inq: %d\n", inq);