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-rw-r--r-- | .gitignore | 56 | ||||
-rw-r--r-- | COPYING | 504 | ||||
-rw-r--r-- | Makefile.am | 4 | ||||
-rw-r--r-- | README.md | 44 | ||||
-rw-r--r-- | configure.ac | 30 | ||||
-rwxr-xr-x | hack/indent.sh | 6 | ||||
-rw-r--r-- | main.c | 312 |
7 files changed, 956 insertions, 0 deletions
diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..e309bbc --- /dev/null +++ b/.gitignore @@ -0,0 +1,56 @@ +slirp4netns +a.out +.deps +*~ +*.log +*.o +config.h +config.status +Makefile +INSTALL + +################################################################################ +# https://github.com/github/gitignore/blob/c24cdc2175d7514d504d7f060a5d69675c8a9b50/Autotools.gitignore +################################################################################ + +# http://www.gnu.org/software/automake + +Makefile.in +/ar-lib +/mdate-sh +/py-compile +/test-driver +/ylwrap + +# http://www.gnu.org/software/autoconf + +autom4te.cache +/autoscan.log +/autoscan-*.log +/aclocal.m4 +/compile +/config.guess +/config.h.in +/config.sub +/configure +/configure.scan +/depcomp +/install-sh +/missing +/stamp-h1 + +# https://www.gnu.org/software/libtool/ + +/ltmain.sh + +# http://www.gnu.org/software/texinfo + +/texinfo.tex + +# http://www.gnu.org/software/m4/ + +m4/libtool.m4 +m4/ltoptions.m4 +m4/ltsugar.m4 +m4/ltversion.m4 +m4/lt~obsolete.m4
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Here is a sample; alter the names: + + Yoyodyne, Inc., hereby disclaims all copyright interest in the + library `Frob' (a library for tweaking knobs) written by James Random Hacker. + + <signature of Ty Coon>, 1 April 1990 + Ty Coon, President of Vice + +That's all there is to it! + + diff --git a/Makefile.am b/Makefile.am new file mode 100644 index 0000000..14f7977 --- /dev/null +++ b/Makefile.am @@ -0,0 +1,4 @@ +bin_PROGRAMS = slirp4netns + +slirp4netns_SOURCES = main.c +slirp4netns_LDADD = -lslirp -lpthread diff --git a/README.md b/README.md new file mode 100644 index 0000000..355dc50 --- /dev/null +++ b/README.md @@ -0,0 +1,44 @@ +# slirp4netns: slirp for network namespaces, without copying buffers across the namespaces + + +## Install + +Requires [libslirp](https://github.com/rd235/libslirp). + +```console +$ autoreconf -if +$ ./configure +$ make +``` + +Or just `cc -o slirp4netns *.c -lslirp -lpthread` + +### Static binary +You can also build a static binary by running `./configure LDFLAGS=-static`. + +Note that you need to install libslirp with `./configure --enable-static`. + +## Usage + +Terminal 1: +```console +$ unshare -r -n -m +unshared$ echo $$ > /tmp/pid +unshared$ ip tuntap add name tap0 mode tap +unshared$ ip link set tap0 up +unshared$ ip addr add 10.0.2.100/24 dev tap0 +unshared$ ip route add default via 10.0.2.2 dev tap0 +unshared$ echo "nameserver 10.0.2.3" > /tmp/resolv.conf +unshared$ mount --bind /tmp/resolv.conf /etc/resolv.conf +``` + +Terminal 2: +```console +$ slirp4netns $(cat /tmp/pid) tap0 +``` + +Terminal 1: +```console +unshared$ ping 10.0.2.2 +unshared$ curl https://example.com +``` diff --git a/configure.ac b/configure.ac new file mode 100644 index 0000000..1512a3c --- /dev/null +++ b/configure.ac @@ -0,0 +1,30 @@ +# -*- Autoconf -*- +# Process this file with autoconf to produce a configure script. + +AC_PREREQ([2.69]) +AC_INIT([FULL-PACKAGE-NAME], [VERSION], [BUG-REPORT-ADDRESS]) +AM_INIT_AUTOMAKE([foreign]) +AC_CONFIG_SRCDIR([main.c]) +AC_CONFIG_HEADERS([config.h]) + +# Checks for programs. +AC_PROG_CC + +# Checks for libraries. +AC_CHECK_LIB([pthread], [pthread_create]) +AC_CHECK_LIB([slirp], [slirp_open]) + +# Checks for header files. +AC_CHECK_HEADERS([fcntl.h stdlib.h string.h sys/ioctl.h sys/socket.h unistd.h]) + +# Checks for typedefs, structures, and compiler characteristics. +AC_TYPE_PID_T +AC_TYPE_SSIZE_T + +# Checks for library functions. +AC_FUNC_FORK +AC_FUNC_MALLOC +AC_CHECK_FUNCS([memset strdup strtol]) + +AC_CONFIG_FILES([Makefile]) +AC_OUTPUT diff --git a/hack/indent.sh b/hack/indent.sh new file mode 100755 index 0000000..5e4f517 --- /dev/null +++ b/hack/indent.sh @@ -0,0 +1,6 @@ +#!/bin/sh +set -ex + +# indent(1): "You must use the â-Tâ option to tell indent the name of all the typenames in your program that are defined by typedef." +indent -linux -l120 -T ssize_t -T pid_t -T SLIRP *.c +rm -f *.c~ @@ -0,0 +1,312 @@ +#define _GNU_SOURCE +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <fcntl.h> +#include <unistd.h> +#include <sched.h> +#include <pthread.h> +#include <sys/ioctl.h> +#include <sys/socket.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <linux/if.h> +#include <linux/if_tun.h> + +#include <libslirp.h> + +static int nsenter(pid_t target_pid) +{ + char userns[32], netns[32]; + int usernsfd, netnsfd; + snprintf(userns, sizeof(userns), "/proc/%d/ns/user", target_pid); + snprintf(netns, sizeof(netns), "/proc/%d/ns/net", target_pid); + if ((usernsfd = open(userns, O_RDONLY)) < 0) { + perror(userns); + return usernsfd; + } + if ((netnsfd = open(netns, O_RDONLY)) < 0) { + perror(netns); + return netnsfd; + } + if (setns(usernsfd, CLONE_NEWUSER) < 0) { + perror("setns(CLONE_NEWUSER)"); + return -1; + } + if (setns(netnsfd, CLONE_NEWNET) < 0) { + perror("setns(CLONE_NEWNET)"); + return -1; + } + return 0; +} + +static int open_tap(const char *tapname) +{ + int fd; + struct ifreq ifr; + if ((fd = open("/dev/net/tun", O_RDWR)) < 0) { + perror("open(\"/dev/net/tun\")"); + return fd; + } + memset(&ifr, 0, sizeof(ifr)); + ifr.ifr_flags = IFF_TAP | IFF_NO_PI; + strncpy(ifr.ifr_name, tapname, sizeof(ifr.ifr_name) - 1); + if (ioctl(fd, TUNSETIFF, (void *)&ifr) < 0) { + perror("ioctl(TUNSETIFF)"); + close(fd); + return -1; + } + return fd; +} + +static int sendfd(int sock, int fd) +{ + ssize_t rc; + struct msghdr msg; + struct cmsghdr *cmsg; + char cmsgbuf[CMSG_SPACE(sizeof(fd))]; + struct iovec iov; + char dummy = '\0'; + memset(&msg, 0, sizeof(msg)); + iov.iov_base = &dummy; + iov.iov_len = 1; + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + msg.msg_control = cmsgbuf; + msg.msg_controllen = sizeof(cmsgbuf); + cmsg = CMSG_FIRSTHDR(&msg); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_RIGHTS; + cmsg->cmsg_len = CMSG_LEN(sizeof(fd)); + memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd)); + msg.msg_controllen = cmsg->cmsg_len; + if ((rc = sendmsg(sock, &msg, 0)) < 0) { + perror("sendmsg"); + } + return rc; +} + +static int child(int sock, pid_t target_pid, const char *tapname) +{ + int rc, tapfd; + if ((rc = nsenter(target_pid)) < 0) { + return rc; + } + if ((tapfd = open_tap(tapname)) < 0) { + return tapfd; + } + if (sendfd(sock, tapfd) < 0) { + close(tapfd); + close(sock); + return -1; + } + fprintf(stderr, "sent tapfd=%d for %s\n", tapfd, tapname); + close(sock); + return 0; +} + +static int recvfd(int sock) +{ + int fd; + ssize_t rc; + struct msghdr msg; + struct cmsghdr *cmsg; + char cmsgbuf[CMSG_SPACE(sizeof(fd))]; + struct iovec iov; + char dummy = '\0'; + memset(&msg, 0, sizeof(msg)); + iov.iov_base = &dummy; + iov.iov_len = 1; + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + msg.msg_control = cmsgbuf; + msg.msg_controllen = sizeof(cmsgbuf); + if ((rc = recvmsg(sock, &msg, 0)) < 0) { + perror("recvmsg"); + return (int)rc; + } + if (rc == 0) { + fprintf(stderr, "the message is empty\n"); + return -1; + } + cmsg = CMSG_FIRSTHDR(&msg); + if (cmsg == NULL || cmsg->cmsg_type != SCM_RIGHTS) { + fprintf(stderr, "the message does not contain fd\n"); + return -1; + } + memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd)); + return fd; +} + +struct slirp2tap_data { + int tapfd, slirpfd; +}; + +#define ETH_BUF_SIZE (65536) + +// TODO: look into whether we can use splice(2). probably we cannot. +static void *slirp2tap_thread(void *p) +{ + ssize_t rc; + struct slirp2tap_data *data = (struct slirp2tap_data *)p; + unsigned char *buf = (unsigned char *)malloc(ETH_BUF_SIZE); + while (1) { + if ((rc = read(data->slirpfd, buf, ETH_BUF_SIZE)) < 0) { + perror("slirp2tap_thread: read"); + free(buf); + exit(EXIT_FAILURE); + } + if ((rc = write(data->tapfd, buf, rc)) < 0) { + perror("slirp2tap_thread: write"); + free(buf); + exit(EXIT_FAILURE); + } + } + /* NOTREACHED */ + free(buf); +} + +static int tap2slirp(SLIRP *slirp, int tapfd) +{ + ssize_t rc; + unsigned char *buf = (unsigned char *)malloc(ETH_BUF_SIZE); + while (1) { + if ((rc = read(tapfd, buf, ETH_BUF_SIZE)) < 0) { + perror("tap2slirp: recv"); + free(buf); + return (int)rc; + } + if ((rc = slirp_send(slirp, buf, rc)) < 0) { + perror("tap2slirp: slirp_send"); + free(buf); + return (int)rc; + } + } + /* NOTREACHED */ + free(buf); + return -1; +} + +static int do_slirp(int tapfd) +{ + int rc; + pthread_t thr; + struct slirp2tap_data thr_data; + int slirpfd; + SLIRP *slirp = slirp_open(SLIRP_IPV4); + if (slirp == NULL) { + perror("slirp_open"); + return -1; + } + if (slirp_start(slirp) < 0) { + perror("slirp_start"); + slirp_close(slirp); + return -1; + } + // slirp fd can't be used for sending packets to the slirp + if ((slirpfd = slirp_fd(slirp)) < 0) { + perror("slirp_fd"); + slirp_close(slirp); + return slirpfd; + } + thr_data.tapfd = tapfd; + thr_data.slirpfd = slirpfd; + if ((rc = pthread_create(&thr, NULL, slirp2tap_thread, &thr_data)) != 0) { + errno = rc; + perror("pthread_create"); + return -1; + } + fprintf(stderr, "READY\n"); + if (tap2slirp(slirp, tapfd) < 0) { + return -1; + } + /* NOTREACHED */ + if ((rc = pthread_join(thr, NULL)) != 0) { + errno = rc; + perror("pthread_join"); + return -1; + } + return 0; +} + +static int parent(int sock) +{ + int rc, tapfd; + if ((tapfd = recvfd(sock)) < 0) { + return tapfd; + } + fprintf(stderr, "received tapfd=%d\n", tapfd); + close(sock); + if ((rc = do_slirp(tapfd)) < 0) { + close(tapfd); + return rc; + } + return 0; +} + +static void usage(const char *argv0) +{ + fprintf(stderr, "Usage: %s PID TAPNAME\n", argv0); +} + +// caller needs to free tapname +static void parse_args(int argc, const char *argv[], pid_t *ptarget_pid, char **tapname) +{ + int target_pid; + if (argc != 3) { + usage(argv[0]); + exit(EXIT_FAILURE); + } + errno = 0; + target_pid = strtol(argv[1], NULL, 10); + if (errno != 0) { + perror("strtol"); + usage(argv[0]); + exit(EXIT_FAILURE); + } + *ptarget_pid = (pid_t)target_pid; + *tapname = strdup(argv[2]); +} + +int main(int argc, const char *argv[]) +{ + int sv[2]; + pid_t target_pid, child_pid; + char *tapname; + parse_args(argc, argv, &target_pid, &tapname); + if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sv) < 0) { + perror("socketpair"); + exit(EXIT_FAILURE); + } + if ((child_pid = fork()) < 0) { + perror("fork"); + free(tapname); + exit(EXIT_FAILURE); + } + if (child_pid == 0) { + if (child(sv[1], target_pid, tapname) < 0) { + exit(EXIT_FAILURE); + } + } else { + int child_wstatus, child_status; + free(tapname); + tapname = NULL; + waitpid(child_pid, &child_wstatus, 0); + if (!WIFEXITED(child_wstatus)) { + fprintf(stderr, "child failed\n"); + exit(EXIT_FAILURE); + } + child_status = WEXITSTATUS(child_wstatus); + if (child_status != 0) { + fprintf(stderr, "child failed(%d)\n", child_status); + exit(child_status); + } + if (parent(sv[0]) < 0) { + fprintf(stderr, "parent failed\n"); + exit(EXIT_FAILURE); + } + } + return 0; +} |