From 72a724f07536cfea7bb9a299cf503143124bd4bd Mon Sep 17 00:00:00 2001 From: Adam Ierymenko Date: Thu, 25 Oct 2018 13:10:24 -0700 Subject: [PATCH] Clean up some stuff after new feth tap implementation, and comment agent file. --- {osdep => attic}/OSXEthernetTap.cpp | 0 {osdep => attic}/OSXEthernetTap.hpp | 0 osdep/MacEthernetTap.cpp | 20 ++++++------ osdep/MacEthernetTapAgent.c | 50 +++++++++++++++++++++++------ 4 files changed, 52 insertions(+), 18 deletions(-) rename {osdep => attic}/OSXEthernetTap.cpp (100%) rename {osdep => attic}/OSXEthernetTap.hpp (100%) diff --git a/osdep/OSXEthernetTap.cpp b/attic/OSXEthernetTap.cpp similarity index 100% rename from osdep/OSXEthernetTap.cpp rename to attic/OSXEthernetTap.cpp diff --git a/osdep/OSXEthernetTap.hpp b/attic/OSXEthernetTap.hpp similarity index 100% rename from osdep/OSXEthernetTap.hpp rename to attic/OSXEthernetTap.hpp diff --git a/osdep/MacEthernetTap.cpp b/osdep/MacEthernetTap.cpp index ec1a56151..92df2f312 100644 --- a/osdep/MacEthernetTap.cpp +++ b/osdep/MacEthernetTap.cpp @@ -111,6 +111,12 @@ MacEthernetTap::MacEthernetTap( freeifaddrs(ifa); } + std::string agentPath(homePath); + agentPath.push_back(ZT_PATH_SEPARATOR); + agentPath.append("MacEthernetTapAgent"); + if (!OSUtils::fileExists(agentPath.c_str())) + throw std::runtime_error("MacEthernetTapAgent not installed in ZeroTier home"); + Mutex::Lock _gl(globalTapCreateLock); // only make one at a time unsigned int devNo = (nwid ^ (nwid >> 32) ^ (nwid >> 48)) % 5000; @@ -123,22 +129,18 @@ MacEthernetTap::MacEthernetTap( } OSUtils::ztsnprintf(devnostr,sizeof(devnostr),"%u",devNo); - if (::pipe(_shutdownSignalPipe)) { + if (::pipe(_shutdownSignalPipe)) throw std::runtime_error("pipe creation failed"); - } int agentStdin[2]; int agentStdout[2]; int agentStderr[2]; - if (::pipe(agentStdin)) { + if (::pipe(agentStdin)) throw std::runtime_error("pipe creation failed"); - } - if (::pipe(agentStdout)) { + if (::pipe(agentStdout)) throw std::runtime_error("pipe creation failed"); - } - if (::pipe(agentStderr)) { + if (::pipe(agentStderr)) throw std::runtime_error("pipe creation failed"); - } _agentStdin = agentStdin[1]; _agentStdout = agentStdout[0]; _agentStderr = agentStderr[0]; @@ -155,7 +157,7 @@ MacEthernetTap::MacEthernetTap( ::close(agentStdin[0]); ::close(agentStdout[1]); ::close(agentStderr[1]); - ::execl(ZT_MACETHERNETTAPAGENT_DEFAULT_SYSTEM_PATH,ZT_MACETHERNETTAPAGENT_DEFAULT_SYSTEM_PATH,devnostr,ethaddr,mtustr,metricstr,(char *)0); + ::execl(agentPath.c_str(),agentPath.c_str(),devnostr,ethaddr,mtustr,metricstr,(char *)0); ::exit(-1); } else { _agentPid = apid; diff --git a/osdep/MacEthernetTapAgent.c b/osdep/MacEthernetTapAgent.c index fe601dbfc..871b3d402 100644 --- a/osdep/MacEthernetTapAgent.c +++ b/osdep/MacEthernetTapAgent.c @@ -24,9 +24,38 @@ * of your own application. */ -/* This is the agent program that is executed with setuid privileges to - * actually manage feth pairs. Its execution in this manner allows ZT - * itself to drop privileges on Mac. */ +/* + * This creates a pair of feth devices with the lower numbered device + * being the ZeroTier virtual interface and the other being the device + * used to actually read and write packets. The latter gets no IP config + * and is only used for I/O. The behavior of feth is similar to the + * veth pairs that exist on Linux. + * + * The feth device has only existed since MacOS Sierra, but that's fairly + * long ago in Mac terms. + * + * I/O with feth must be done using two different sockets. The BPF socket + * is used to receive packets, while an AF_NDRV (low-level network driver + * access) socket must be used to inject. AF_NDRV can't read IP frames + * since BSD doesn't forward packets out the NDRV tap if they've already + * been handled, and while BPF can inject its MTU for injected packets + * is limited to 2048. AF_NDRV packet injection is required to inject + * ZeroTier's large MTU frames. + * + * Benchmarks show that this performs similarly to the old tap.kext driver, + * and a kext is no longer required. Splitting it off into an agent will + * also make it easier to have zerotier-one itself drop permissions. + * + * All this stuff is basically undocumented. A lot of tracing through + * the Darwin/XNU kernel source was required to figure out how to make + * this actually work. + * + * See also: + * + * https://apple.stackexchange.com/questions/337715/fake-ethernet-interfaces-feth-if-fake-anyone-ever-seen-this + * https://opensource.apple.com/source/xnu/xnu-4570.41.2/bsd/net/if_fake.c.auto.html + * + */ #include #include @@ -80,6 +109,7 @@ static unsigned char s_stdinReadBuf[262144] __attribute__ ((__aligned__(16))); static char s_deviceName[IFNAMSIZ]; static char s_peerDeviceName[IFNAMSIZ]; static int s_bpffd = -1; +static int s_ndrvfd = -1; static pid_t s_parentPid; static void configureIpv6Parameters(const char *ifname,int performNUD,int acceptRouterAdverts) @@ -154,6 +184,8 @@ static int run(const char *path,...) static void die() { + if (s_ndrvfd >= 0) + close(s_ndrvfd); if (s_bpffd >= 0) close(s_bpffd); if (s_deviceName[0]) @@ -207,8 +239,8 @@ int main(int argc,char **argv) const char *mtu = argv[3]; const char *metric = argv[4]; - int ndrvSocket = socket(AF_NDRV,SOCK_RAW,0); - if (ndrvSocket < 0) { + s_ndrvfd = socket(AF_NDRV,SOCK_RAW,0); + if (s_ndrvfd < 0) { fprintf(stderr,"E unable to open AF_NDRV socket\n"); return ZT_MACETHERNETTAPAGENT_EXIT_CODE_UNABLE_TO_CREATE; } @@ -239,11 +271,11 @@ int main(int argc,char **argv) nd.snd_len = sizeof(struct sockaddr_ndrv); nd.snd_family = AF_NDRV; memcpy(nd.snd_name,s_peerDeviceName,sizeof(nd.snd_name)); - if (bind(ndrvSocket,(struct sockaddr *)&nd,sizeof(nd)) != 0) { + if (bind(s_ndrvfd,(struct sockaddr *)&nd,sizeof(nd)) != 0) { fprintf(stderr,"E unable to bind AF_NDRV socket\n"); return ZT_MACETHERNETTAPAGENT_EXIT_CODE_UNABLE_TO_CREATE; } - if (connect(ndrvSocket,(struct sockaddr *)&nd,sizeof(nd)) != 0) { + if (connect(s_ndrvfd,(struct sockaddr *)&nd,sizeof(nd)) != 0) { fprintf(stderr,"E unable to connect AF_NDRV socket\n"); return ZT_MACETHERNETTAPAGENT_EXIT_CODE_UNABLE_TO_CREATE; } @@ -291,7 +323,7 @@ int main(int argc,char **argv) } fcntl(STDIN_FILENO,F_SETFL,fcntl(STDIN_FILENO,F_GETFL)|O_NONBLOCK); - fcntl(ndrvSocket,F_SETFL,fcntl(ndrvSocket,F_GETFL)|O_NONBLOCK); + fcntl(s_ndrvfd,F_SETFL,fcntl(s_ndrvfd,F_GETFL)|O_NONBLOCK); fcntl(s_bpffd,F_SETFL,fcntl(s_bpffd,F_GETFL)|O_NONBLOCK); fprintf(stderr,"I %s %s %d.%d.%d.%d\n",s_deviceName,s_peerDeviceName,ZEROTIER_ONE_VERSION_MAJOR,ZEROTIER_ONE_VERSION_MINOR,ZEROTIER_ONE_VERSION_REVISION,ZEROTIER_ONE_VERSION_BUILD); @@ -340,7 +372,7 @@ int main(int argc,char **argv) switch(msg[0]) { case ZT_MACETHERNETTAPAGENT_STDIN_CMD_PACKET: if (len > 1) { - if (write(ndrvSocket,msg+1,len-1) < 0) { + if (write(s_ndrvfd,msg+1,len-1) < 0) { fprintf(stderr,"E inject failed size==%ld errno==%d\n",len-1,errno); } }