June 2005 - Darwin-dev - lists.apple.com

Re: ICMP Router Discovery
by Justin C. Walker 29 Jun '05

29 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On Jun 28, 2005, at 17:10 , Chase wrote: Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large Institute for General Semantics -------- If you're not confused, You're not paying attention -------- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… the bottom line is that i need **all routers** and everything that interacts with the routing table that i've seen so far only acknowledges the **default** router. Then the bottom line for you is that you may not get to your goal (what ever that is). and netstat does not display all the router addresses on the network. it only displays the address of the default router. 'netstat' only tells you what your local routing database tells you. Your local routing database gets input from a number of sources, but for your typical workstation, this information comes either from local manual configuration, or from DHCP/BootP. There's nothing dynamic about it. someone else chimed in earlier saying the same thing, but it simply doesn't do it, at least not with the arguments he had suggested and not with any of the arguments that i've tried previously or since. We're all just shooting in the dark, since you haven't told us what your goal is. note: on another list, someone pointed out that this info can be obtained using the SystemConfiguration apis. i've figured out how to get it that way and it works fine, but it isn't portable to other operating systems, obviously. since the first release of this app is for mac os only, for the time being, i'll be using that technique, but i still want to find out **some** way of doing this in a platform-agnostic way for possible future ports. Each platform has a way to store this information and retrieve it during startup (e.g., /etc/iftab). But again, it's generally static information that has been hand-configured (e.g., set up on the DHCP server, and forgotten), and there is no dynamic way for a workstation to discover all the routers in the neighborhood. This email sent to site_archiver(a)lists.apple.com

1 0

Re: pthread_cond_timedwait() bug in Tiger?
by Matt Watson 29 Jun '05

29 Jun '05

site_archiver(a)lists.apple.com Delivered-To: Darwin-dev(a)lists.apple.com For posterity: matt. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Could it be that there is a bug in pthread_cond_timedwait() that causes it to block forever if the absolute time value passed to it lies in the past? Hi, sorry for taking so long to follow up with this. I've been a little busy. Yes, there appears to be a bug in this routine in Tiger when either _XOPEN_SOURCE, _POSIX_C_SOURCE or _APPLE_C_SOURCE is defined at compile time, and you pass in an already elapsed timeout at runtime. As a workaround, you can use pthread_cond_timedwait_relative_np() and pass in a relative timeout, rather than computing the absolute timeout. This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Justin C. Walker 29 Jun '05

29 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On Jun 28, 2005, at 16:02 , Chase wrote: the responses from the one router were provoked by pinging 224.0.0.9 Visit this site for a listing of multicast address assignments: <http://www.iana.org/assignments/multicast-addresses> What Peter said. Can you describe your goals? Cheers, Justin -- Justin C. Walker, Curmudgeon-At-Large Institute for General Semantics -------- Men are from Earth. Women are from Earth. Deal with it. -------- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Pinging 224.0.0.2 should get replies from everything that thinks its a router and cares for answering. hmmm... just tried "ping 224.0.0.2", but it just hangs there, getting no reponses from anything. i like this idea though (in terms of portability). can you help me figure out what i'm doing wrong? i tried pinging 224.0.0.0 thru 224.0.0.100 (and a few toward the top of the range as well), and i could get responses from one of the routers, but not the other. but, again, the other router didn't respond to any of the 224.0.0.xxx pings. Note that there will, on any given network, likely be a variety of routing protocols, and routers, running. Not all will respond to a given protocol, and not all will respond to the kind of nudging you are doing. BUT... i tried pinging 192.168.0.255 and 192.168.1.255 and i got something very interesting and useful: PING 192.168.0.255 (192.168.0.255): 56 data bytes I assume you are sending to the subnet broadcast address, so you are effectively broadcasting the 'ping'. this is great. i'm not complaining at all. quite the contrary. but, could someone explain why no other hosts on the subnet(s) are responding? i'm obviously missing something key to how messages are broadcast locally. Not all hosts will respond to broadcast pings (to avoid some kinds of DOS attacks). BSD-derived systems have a knob to control this ("sysctl net.inet.icmp.bmcastecho"). This knob controls the system's response to both broadcast and multicast pings (cf. above). if this turns out to be consistently predictable (pinging the broadcast address of the subnet yields **ONLY** results from oneself and the router on that subnet), then i can just look thru the ping source, pull out the relevant parts, and simply filter out responses from the local address. that should always give me the router address, right? This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Chase 29 Jun '05

29 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com - chase _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… i have been eyebrows-deep in the route source code for two weeks now (and, of course, the manpage too). the bottom line is that i need **all routers** and everything that interacts with the routing table that i've seen so far only acknowledges the **default** router. you may be right, but you weren't specific enough to convince me of anything. and netstat does not display all the router addresses on the network. it only displays the address of the default router. someone else chimed in earlier saying the same thing, but it simply doesn't do it, at least not with the arguments he had suggested and not with any of the arguments that i've tried previously or since. if you know how to get netstat to display the router addresses for all connected networks, i'd love to know too. :) note: on another list, someone pointed out that this info can be obtained using the SystemConfiguration apis. i've figured out how to get it that way and it works fine, but it isn't portable to other operating systems, obviously. since the first release of this app is for mac os only, for the time being, i'll be using that technique, but i still want to find out **some** way of doing this in a platform- agnostic way for possible future ports. also note: i just found out that windows machines don't respond to broadcast pings, which would explain why all i received back was my address and the address of the router (all the other machines on both lans are running windows). so that's out the door i guess. This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Peter Bierman 28 Jun '05

28 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com I think you're going down the wrong track. Instead, you need to think about what it means to have a router at all. When the given machine needs to talk to other machines, it uses an address. So you can get the information you want without asking the network anything. Take a long look at: 'man 4 route' -pmb _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… At 6:02 PM -0500 6/28/05, Chase wrote: if this turns out to be consistently predictable (pinging the broadcast address of the subnet yields **ONLY** results from oneself and the router on that subnet), then i can just look thru the ping source, pull out the relevant parts, and simply filter out responses from the local address. that should always give me the router address, right? Routers may or may not have certain behaviors that you can use to identify them, but those behaviors might be different and change over time. You have a given machine connected to any number of networks. There are other devices connected to those networks. Some of those devices might not be final destinations, but instead will forward traffic. First, it checks to see if that address lives on a network already connected to itself. If it is, then it picks the interface holding that network, and sends the data directly there. No router is used. If the destination address is NOT on a directly connected network, it starts looking for a 'gateway'. Gateways are machines on a directly connected network that will accept traffic for networks beyond. AKA, routers. There might be gateways that are only valid for a range of IPs. And there will almost always be one gateway that's valid for any IP; that's the default route/gateway. They're checked from most-specific to least specific. netstat knows a list of the valid gateways. It has to, since your machine can't use routers it doesn't know about! This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Chase 28 Jun '05

28 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com okay, i just played around a little with this. the responses from the one router were provoked by pinging 224.0.0.9 PING 192.168.0.255 (192.168.0.255): 56 data bytes 64 bytes from 192.168.0.102: icmp_seq=0 ttl=64 time=0.180 ms 64 bytes from 192.168.0.250: icmp_seq=0 ttl=64 time=1.905 ms (DUP!) 64 bytes from 192.168.0.102: icmp_seq=1 ttl=64 time=0.177 ms 64 bytes from 192.168.0.250: icmp_seq=1 ttl=64 time=1.512 ms (DUP!) 64 bytes from 192.168.0.102: icmp_seq=2 ttl=64 time=0.168 ms 64 bytes from 192.168.0.250: icmp_seq=2 ttl=64 time=1.723 ms (DUP!) 64 bytes from 192.168.0.102: icmp_seq=3 ttl=64 time=0.176 ms 64 bytes from 192.168.0.250: icmp_seq=3 ttl=64 time=1.506 ms (DUP!) 64 bytes from 192.168.0.102: icmp_seq=4 ttl=64 time=0.174 ms 64 bytes from 192.168.0.250: icmp_seq=4 ttl=64 time=1.648 ms (DUP!) PING 192.168.1.255 (192.168.1.255): 56 data bytes 64 bytes from 192.168.1.104: icmp_seq=0 ttl=64 time=0.295 ms 64 bytes from 192.168.1.250: icmp_seq=0 ttl=150 time=4.961 ms (DUP!) 64 bytes from 192.168.1.250: icmp_seq=0 ttl=150 time=32.736 ms (DUP!) 64 bytes from 192.168.1.104: icmp_seq=1 ttl=64 time=0.265 ms 64 bytes from 192.168.1.250: icmp_seq=1 ttl=150 time=5.069 ms (DUP!) 64 bytes from 192.168.1.104: icmp_seq=2 ttl=64 time=0.281 ms 64 bytes from 192.168.1.250: icmp_seq=2 ttl=150 time=4.240 ms (DUP!) 64 bytes from 192.168.1.104: icmp_seq=3 ttl=64 time=0.265 ms 64 bytes from 192.168.1.250: icmp_seq=3 ttl=150 time=4.276 ms (DUP!) for each icmp_seq, there is a single pair: my ip (192.168._.10_) router ip (192.168._.250) (not always in that order). thanks. - chase _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Pinging 224.0.0.2 should get replies from everything that thinks its a router and cares for answering. I'm not sure if it helps but it's something... Of course you still wouldn't get the routes they're routing. hmmm... just tried "ping 224.0.0.2", but it just hangs there, getting no reponses from anything. i like this idea though (in terms of portability). can you help me figure out what i'm doing wrong? i tried pinging 224.0.0.0 thru 224.0.0.100 (and a few toward the top of the range as well), and i could get responses from one of the routers, but not the other. but, again, the other router didn't respond to any of the 224.0.0.xxx pings. BUT... i tried pinging 192.168.0.255 and 192.168.1.255 and i got something very interesting and useful: there are other hosts on both LANs and yet none of those hosts are responding. this is great. i'm not complaining at all. quite the contrary. but, could someone explain why no other hosts on the subnet(s) are responding? i'm obviously missing something key to how messages are broadcast locally. if this turns out to be consistently predictable (pinging the broadcast address of the subnet yields **ONLY** results from oneself and the router on that subnet), then i can just look thru the ping source, pull out the relevant parts, and simply filter out responses from the local address. that should always give me the router address, right? This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Chase 28 Jun '05

28 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On Jun 28, 2005, at 4:30 PM, Pelle Johansson wrote: 28 jun 2005 kl. 19.09 skrev Chase: i need them all. thanks. - chase _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Pinging 224.0.0.2 should get replies from everything that thinks its a router and cares for answering. I'm not sure if it helps but it's something... Of course you still wouldn't get the routes they're routing. hmmm... just tried "ping 224.0.0.2", but it just hangs there, getting no reponses from anything. i like this idea though (in terms of portability). can you help me figure out what i'm doing wrong? This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Pelle Johansson 28 Jun '05

28 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com 28 jun 2005 kl. 19.09 skrev Chase: i need them all. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Pinging 224.0.0.2 should get replies from everything that thinks its a router and cares for answering. I'm not sure if it helps but it's something... Of course you still wouldn't get the routes they're routing. -- Pelle Johansson <morth(a)morth.org> This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Justin C. Walker 28 Jun '05

28 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On Jun 28, 2005, at 10:40 , Chase wrote: default 172.31.128.254 UGSc 3 103 en0 172.31.192/19 172.31.128.254 UGSc 2 4 en0 route add default 192.168.0.250 Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large Institute for General Semantics -------- "Weaseling out of things is what separates us from the animals. Well, except the weasel." - Homer J Simpson -------- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Actually, it should show you all the gateways, not just the default route: G RTF_GATEWAY Destination requires forwarding by intermediary I thought that's what you said you wanted, maybe I was mistaken. From my machine: I think this shows that traffic using the default route, as well as any traffic to a destination in the range "172.31.192/19", uses the router 172.31.128.254; that is the gateway for both. [snip] I've tried this in the past and I tried again just now. It only shows the default router address. There is absolutely no mention of the other router ip address in the netstat output. There is a difference between the routers that are "out there", the routers that the system knows about (in the routing table), and the routers that are known about but only in a database somewhere. The information kept by the SystemConfiguration framework, as in your case, is only acted on when the corresponding interface is the "primary". This is determined by the ordering of the interfaces in the network prefs panel (in the "show" popup, select network port configuration; you can enable, disable, and reorder the interfaces shown there). Thus, a router associated to en0 will only be added to the routing database in the kernel when en0 is the highest interface in the above list that is enabled (checked) and active (has a signal (e.g., a cable plugged in)). By the way: I just accidentally deleted all my routes and lost internet connectivity by running "route flush". The only thing I could think of to do was: ...which seems to have worked. Would a reboot have fixed that problem As Andrew suggests, removing and replacing the cable, or enabling and disabling the interface (in the network prefs panel), should suffice. Rebooting a Mac OS X system is generally not needed, unless the software changes in some significant way (or cosmic rays intervene :-}). This email sent to site_archiver(a)lists.apple.com

1 0

Re: ICMP Router Discovery
by Andrew Gallatin 28 Jun '05

28 Jun '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Chase writes: > > I've tried this in the past and I tried again just now. It only > shows the default router address. There is absolutely no mention of > the other router ip address in the netstat output. Interesting. Netstat has lots of flags. Keep adding them until you find what you're looking for (maybe its RTF_PRCLONING with -a). > > By the way: I just accidentally deleted all my routes and lost > internet connectivity by running "route flush". The only thing I > could think of to do was: > > route add default 192.168.0.250 > > ...which seems to have worked. Would a reboot have fixed that > problem, since the routing table is adjusted dynamically? If not, > what's the recommended way to get the defaults back to normal again? > Is "route add default <router_ip>" an incomplete fix in any way? I'd just unplug/replug the cable, or turn off/on the airport interface. Drew _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

1 0