net: new module to help IPv4/IPv6 transition.

ccan/net/LICENSE

@@ -0,0 +1 @@
+../../licenses/BSD-MIT

ccan/net/_info

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+#include <string.h>
+#include "config.h"
+
+/**
+ * net - simple IPv4/IPv6 client library
+ *
+ * This code makes it simple to support IPv4 and IPv6 without speed penalty.
+ *
+ * License: MIT
+ *
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ *
+ * Example:
+ *	#include <ccan/net/net.h>
+ *	#include <sys/types.h>
+ *	#include <sys/socket.h>
+ *	#include <stdio.h>
+ *	#include <err.h>
+ *
+ *	int main(int argc, char *argv[])
+ *	{
+ *		struct addrinfo *addr;
+ *		const char *dest, *port;
+ *		int fd;
+ *		struct sockaddr saddr;
+ *		socklen_t slen = sizeof(saddr);
+ *	
+ *		if (argc == 2) {
+ *			dest = argv[1];
+ *			port = "http";
+ *		} else if (argc == 3) {
+ *			dest = argv[1];
+ *			port = argv[2];
+ *		} else
+ *			errx(1, "Usage: test-net <target> [<port>]");
+ *	
+ *		addr = net_client_lookup(dest, port, AF_UNSPEC, SOCK_STREAM);
+ *		if (!addr)
+ *			err(1, "Failed to look up %s", dest);
+ *	
+ *		fd = net_connect(addr);
+ *		if (fd < 0)
+ *			err(1, "Failed to connect to %s", dest);
+ *	
+ *		if (getsockname(fd, &saddr, &slen) == 0)
+ *			printf("Connected via %s\n",
+ *			       saddr.sa_family == AF_INET6 ? "IPv6"
+ *			       : saddr.sa_family == AF_INET ? "IPv4"
+ *			       : "UNKNOWN??");
+ *		else
+ *			err(1, "Failed to get socket type for connection");
+ *		return 0;
+ *	}
+ */
+int main(int argc, char *argv[])
+{
+	/* Expect exactly one argument */
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		printf("ccan/noerr\n");
+		return 0;
+	}
+
+	return 1;
+}

ccan/net/net.c

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+#include <ccan/net/net.h>
+#include <ccan/noerr/noerr.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <poll.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdbool.h>
+
+struct addrinfo *net_client_lookup(const char *hostname,
+				   const char *service,
+				   int family,
+				   int socktype)
+{
+	struct addrinfo hints;
+	struct addrinfo *res;
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = family;
+	hints.ai_socktype = socktype;
+	hints.ai_flags = 0;
+	hints.ai_protocol = 0;
+
+	if (getaddrinfo(hostname, service, &hints, &res) != 0)
+		return NULL;
+
+	return res;
+}
+
+static bool set_nonblock(int fd, bool nonblock)
+{
+	long flags;
+
+	flags = fcntl(fd, F_GETFL);
+	if (flags == -1)
+		return false;
+
+	if (nonblock)
+		flags |= O_NONBLOCK;
+	else
+		flags &= ~(long)O_NONBLOCK;
+
+	return (fcntl(fd, F_SETFL, flags) == 0);
+}
+
+/* We only handle IPv4 and IPv6 */
+#define MAX_PROTOS 2
+
+static void remove_fd(struct pollfd pfd[],
+		      const struct addrinfo *addr[],
+		      socklen_t slen[],
+		      unsigned int *num,
+		      unsigned int i)
+{
+	memmove(pfd + i, pfd + i + 1, (*num - i - 1) * sizeof(pfd[0]));
+	memmove(addr + i, addr + i + 1, (*num - i - 1) * sizeof(addr[0]));
+	memmove(slen + i, slen + i + 1, (*num - i - 1) * sizeof(slen[0]));
+	(*num)--;
+}
+
+int net_connect(const struct addrinfo *addrinfo)
+{
+	int sockfd = -1;
+	unsigned int i, num;
+	const struct addrinfo *ipv4 = NULL, *ipv6 = NULL;
+	const struct addrinfo *addr[MAX_PROTOS];
+	socklen_t slen[MAX_PROTOS];
+	struct pollfd pfd[MAX_PROTOS];
+
+	for (; addrinfo; addrinfo = addrinfo->ai_next) {
+		switch (addrinfo->ai_family) {
+		case AF_INET:
+			if (!ipv4)
+				ipv4 = addrinfo;
+			break;
+		case AF_INET6:
+			if (!ipv6)
+				ipv6 = addrinfo;
+			break;
+		}
+	}
+
+	num = 0;
+	/* We give IPv6 a slight edge by connecting it first. */
+	if (ipv6) {
+		addr[num] = ipv6;
+		slen[num] = sizeof(struct sockaddr_in6);
+		pfd[num].fd = socket(AF_INET6, ipv6->ai_socktype,
+				     ipv6->ai_protocol);
+		if (pfd[num].fd != -1)
+			num++;
+	}
+	if (ipv4) {
+		addr[num] = ipv4;
+		slen[num] = sizeof(struct sockaddr_in);
+		pfd[num].fd = socket(AF_INET, ipv4->ai_socktype,
+				     ipv4->ai_protocol);
+		if (pfd[num].fd != -1)
+			num++;
+	}
+
+	for (i = 0; i < num; i++) {
+		if (!set_nonblock(pfd[i].fd, true)) {
+			remove_fd(pfd, addr, slen, &num, i--);
+			continue;
+		}
+		/* Connect *can* be instant. */
+		if (connect(pfd[i].fd, addr[i]->ai_addr, slen[i]) == 0)
+			goto got_one;
+		if (errno != EINPROGRESS) {
+			/* Remove dead one. */
+			remove_fd(pfd, addr, slen, &num, i--);
+		}
+		pfd[i].events = POLLOUT;
+	}
+
+	while (num && poll(pfd, num, -1) != -1) {
+		for (i = 0; i < num; i++) {
+			int err;
+			socklen_t errlen = sizeof(err);
+			if (!pfd[i].revents)
+				continue;
+			if (getsockopt(pfd[i].fd, SOL_SOCKET, SO_ERROR, &err,
+				       &errlen) != 0)
+				goto out;
+			if (err == 0)
+				goto got_one;
+
+			/* Remove dead one. */
+			errno = err;
+			remove_fd(pfd, addr, slen, &num, i--);
+		}
+	}
+
+got_one:
+	/* We don't want to hand them a non-blocking socket! */
+	if (set_nonblock(pfd[i].fd, false))
+		sockfd = pfd[i].fd;
+
+out:
+	for (i = 0; i < num; i++)
+		if (pfd[i].fd != sockfd)
+			close_noerr(pfd[i].fd);
+	return sockfd;
+}

ccan/net/net.h

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+#ifndef CCAN_NET_H
+#define CCAN_NET_H
+/**
+ * net_client_lookup - look up a network name to connect to.
+ * @hostname: the name to look up
+ * @service: the service to look up
+ * @family: Usually AF_UNSPEC, otherwise AF_INET or AF_INET6.
+ * @socktype: SOCK_DGRAM or SOCK_STREAM.
+ *
+ * This will do a synchronous lookup of a given name, returning a linked list
+ * of results, or NULL on error.  You should use freeaddrinfo() to free it.
+ *
+ * Example:
+ *	#include <sys/types.h>
+ *	#include <sys/socket.h>
+ *	#include <stdio.h>
+ *	#include <netdb.h>
+ *	#include <err.h>
+ *	...
+ *	struct addrinfo *addr;
+ *
+ *	// Get a TCP connection to ccan.ozlabs.org daytime port.
+ *	addr = net_client_lookup("ccan.ozlabs.org", "daytime",
+ *				 AF_UNSPEC, SOCK_STREAM);
+ *	if (!addr)
+ *		errx(1, "Failed to look up daytime at ccan.ozlabs.org");
+ */
+struct addrinfo *net_client_lookup(const char *hostname,
+				   const char *service,
+				   int family,
+				   int socktype);
+
+/**
+ * net_connect - connect to a server
+ * @addrinfo: linked list struct addrinfo (usually from net_client_lookup).
+ *
+ * This synchronously connects to a server described by @addrinfo, or returns
+ * -1 on error (and sets errno).
+ *
+ * Example:
+ *	int fd;
+ *	...
+ *	fd = net_connect(addr);
+ *	if (fd < 0)
+ *		err(1, "Failed to connect to ccan.ozlabs.org");
+ *	freeaddrinfo(addr);
+ */
+int net_connect(const struct addrinfo *addrinfo);
+#endif /* CCAN_NET_H */

ccan/net/test/run.c

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+#include <ccan/net/net.h>
+#include <ccan/net/net.c>
+#include <ccan/tap/tap.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <err.h>
+
+static unsigned int server(int protocol, int type)
+{
+	int sock;
+	union {
+		struct sockaddr addr;
+		struct sockaddr_in ipv4;
+		struct sockaddr_in6 ipv6;
+	} addr;
+	socklen_t addlen = sizeof(addr);
+
+	sock = socket(protocol, type, 0);
+
+	/* Bind to free port. */
+	listen(sock, 0);
+
+	/* Figure out what port it gave us. */
+	getsockname(sock, &addr.addr, &addlen);
+	fflush(stdout);
+
+	if (fork() == 0) {
+		int ret, fd;
+
+		alarm(3);
+		fd = accept(sock, NULL, 0);
+		if (fd < 0)
+			err(1, "Accepting from socket %i", sock);
+
+		ret = write(fd, "Yay!", strlen("Yay!"));
+		if (ret != strlen("Yay!"))
+			err(1, "Write returned %i", ret);
+		exit(0);
+	}
+	close(sock);
+	return ntohs(protocol == AF_INET
+		     ? addr.ipv4.sin_port : addr.ipv6.sin6_port);
+}
+
+int main(void)
+{
+	struct addrinfo *addr, *addr2;
+	int fd, status;
+	struct sockaddr saddr;
+	socklen_t slen = sizeof(saddr);
+	char buf[20];
+	unsigned int port;
+
+	plan_tests(16);
+	port = server(AF_INET, SOCK_STREAM);
+	sprintf(buf, "%u", port);
+
+	addr = net_client_lookup("localhost", buf, AF_UNSPEC, SOCK_STREAM);
+	addr2 = net_client_lookup("ip6-localhost", buf,
+				  AF_UNSPEC, SOCK_STREAM);
+	ok1(addr);
+	ok1(addr2);
+	/* Join them as if they were from one lookup. */
+	addr->ai_next = addr2;
+
+	fd = net_connect(addr);
+	ok1(fd >= 0);
+
+	ok1(getsockname(fd, &saddr, &slen) == 0);
+	ok1(saddr.sa_family == AF_INET);
+	status = read(fd, buf, sizeof(buf));
+	ok(status == strlen("Yay!"),
+	   "Read returned %i (%s)", status, strerror(errno));
+	ok1(strncmp(buf, "Yay!", strlen("Yay!")) == 0);
+	close(fd);
+	addr->ai_next = NULL;
+	freeaddrinfo(addr);
+	freeaddrinfo(addr2);
+
+	port = server(AF_INET6, SOCK_STREAM);
+	sprintf(buf, "%u", port);
+
+	addr = net_client_lookup("localhost", buf, AF_UNSPEC, SOCK_STREAM);
+	addr2 = net_client_lookup("ip6-localhost", buf,
+				  AF_UNSPEC, SOCK_STREAM);
+	ok1(addr);
+	ok1(addr2);
+	/* Join them as if they were from one lookup. */
+	addr->ai_next = addr2;
+
+	fd = net_connect(addr);
+	ok1(fd >= 0);
+
+	ok1(getsockname(fd, &saddr, &slen) == 0);
+	ok1(saddr.sa_family == AF_INET6);
+	status = read(fd, buf, sizeof(buf));
+	ok(status == strlen("Yay!"),
+	   "Read returned %i (%s)", status, strerror(errno));
+	ok1(strncmp(buf, "Yay!", strlen("Yay!")) == 0);
+	close(fd);
+	addr->ai_next = NULL;
+	freeaddrinfo(addr);
+	freeaddrinfo(addr2);
+
+	wait(&status);
+	ok1(WIFEXITED(status));
+	ok1(WEXITSTATUS(status) == 0);
+
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}

ccan/net/tools/Makefile

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+CFLAGS=-g -Wall -W -I../../..
+
+test-net: test-net.o net.o noerr.o
+
+net.o: ../net.c
+	$(COMPILE.c) $(OUTPUT_OPTION) $<
+
+noerr.o: ../../noerr/noerr.c
+	$(COMPILE.c) $(OUTPUT_OPTION) $<

ccan/net/tools/test-net.c

@@ -0,0 +1,56 @@
+#include <ccan/net/net.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <stdio.h>
+#include <err.h>
+
+static unsigned int count_addrs(const struct addrinfo *addr, int family)
+{
+	unsigned int num = 0;
+
+	while (addr) {
+		if (family == AF_UNSPEC || family == addr->ai_family)
+			num++;
+		addr = addr->ai_next;
+	}
+	return num;
+}
+
+int main(int argc, char *argv[])
+{
+	struct addrinfo *addr;
+	const char *dest, *port;
+	int fd;
+	struct sockaddr saddr;
+	socklen_t slen = sizeof(saddr);
+
+	if (argc == 2) {
+		dest = argv[1];
+		port = "http";
+	} else if (argc == 3) {
+		dest = argv[1];
+		port = argv[2];
+	} else
+		errx(1, "Usage: test-net <target> [<port>]");
+
+	addr = net_client_lookup(dest, port, AF_UNSPEC, SOCK_STREAM);
+	if (!addr)
+		err(1, "Failed to look up %s", dest);
+
+	printf("Received %u IPv4 addresses, %u IPv6 addresses\n",
+	       count_addrs(addr, AF_INET), count_addrs(addr, AF_INET6));
+
+	fd = net_connect(addr);
+	if (fd < 0)
+		err(1, "Failed to connect to %s", dest);
+
+	if (getsockname(fd, &saddr, &slen) == 0)
+		printf("Connected via %s\n",
+		       saddr.sa_family == AF_INET6 ? "IPv6"
+		       : saddr.sa_family == AF_INET ? "IPv4"
+		       : "UNKNOWN??");
+	else
+		err(1, "Failed to get socket type for connection");
+	return 0;
+}