8 ms·

Sorry, not to be rude but in this case is sounds like you don't understand the problem domain. Perhaps I should have just said "UDP spoofing". There is a huge

Sorry, not to be rude but in this case is sounds like you don't understand the problem domain. Perhaps I should have just said "UDP spoofing". There is a huge difference between creating a generic UDP endpoint like the code you have shown, and crafting a raw UDP socket, where the source IP address is "spoofed", and UDP checksums generated to ensure that the packet looks like a valid UDP packet so that the intermediate network infrastructure like routers, switches and firewalls will pass the forged packet rather than discarding it. The latter requires quite a bit of extra code. A good example is here: https://www.binarytides.com/raw-udp-sockets-c-linux/ https://www.binarytides.com/raw-udp-sockets-c-linux/ and last time I looked (month or so ago?) I could not find an equivalent example for Rust. It may be out there but I was unable to locate it. I'm not asking you to do my homework for me, just stating that learning what I need to know in Rust to do the above would take more time than I have available right now. That's not to say I won't figure it out in the future when I have more time. > If you don't know how to do it because you don't know Rust, then fine, that's reasonable. (Albeit a strange criticism to lodge from my perspective.) It's not a criticism of the language; what I'm asking may be very possible, I don't know yet. I just know that finding C examples is trivial, Rust examples not so much, so when I had a need for this kind of code recently, I turned to the language where I know it can be done and I could easily find examples.

woah 7y ago
The specific task is so obscure, that only a language as widespread as C would have an example online for it. So people are confused when you name this as a criteria for selecting a language, since it’s a criteria that most likely only C can satisfy. Then someone jumped to the conclusion that you were actually saying that Rust doesn’t have enough low level kernel APIs because that would make sense.
- nineteen999 7y ago
  > The specific task is so obscure, that only a language as widespread as C would have an example online for it. Well you could do it in Python I suppose - here's someone mentioning a solution using scapy, although it likely wouldn't work too well for my particular case due to Python performance. https://stackoverflow.com/questions/51311741/generating-a-spoofed-udp-packet-in-python https://stackoverflow.com/questions/51311741/generating-a-sp... > So people are confused when you name this as a criteria for selecting a language, since it’s a criteria that most likely only C can satisfy Rust is intended to be a replacement for C and C++, no? Eventually it will need to be able to do things like this if it is to be effective in that role. It's OK in my mind if it is not mature enough to do these kind of tasks yet, or if it can but I can't find a good reference yet. I wanted to use it for this task, but I selected C instead since it was easy to do that way and I didn't have a lot of time. Not holding it against Rust, it's a much younger language. > Then someone jumped to the conclusion that you were actually saying that Rust doesn’t have enough low level kernel APIs because that would make sense. I am almost completely certain I don't understand this sentence the way it is phrased.
  - woah 7y ago
    Example code (for ARP though): https://github.com/libpnet/libpnet/blob/master/examples/arp_packet.rs https://github.com/libpnet/libpnet/blob/master/examples/arp_... Documentation: https://docs.rs/pnet/0.22.0/pnet/packet/udp/struct.MutableUdpPacket.html https://docs.rs/pnet/0.22.0/pnet/packet/udp/struct.MutableUd...
    - nineteen999 7y ago
      Thanks for this, those do look very helpful.
  - rixed 7y ago
    In case you want to give OCaml a try one day, I've done plenty of stuff like that in the past when I needed a (much) faster scappy. UDP exemple here: https://github.com/rixed/robinet/blob/master/udp.ml https://github.com/rixed/robinet/blob/master/udp.ml
    - nineteen999 7y ago
      I'm not really a career programmer or language enthusiast, rather, I'm more of a utilitarian/imperative coder - I write programs to plug gaps in existing infrastructure as quickly, as securely, and as future-proofed as possible, even if it means dumbing the code down somewhat. So I think my head would explode if I tried to learn a FP language without being able to have months off work to study. In addition to that, my team would kill me, as it's hard enough to find good C/C++ programmers in my city, let alone something like OCaml. Given that we run emergency services infrastructure, unfortunately we have to use more popular languages to ensure that the business doesn't end up with a lot of code written in languages they can't support. Regardless, thank you very much for the example. It's nice to see that this can be done in other languages even if I can't understand it. Unfortunately too many years of C/C++ have made it hard for me to grok FP code - the C example I posted up before is much more readable to me.
      - ernst_klim 7y ago
burntsushi 7y ago
Yeah, I mean, as I mentioned, I hadn't done it before. I feel like I've put an appropriate amount of uncertainty in my comments, but I still feel like you're punishing me for it. In any case, I don't see anything particularly interesting in that C code. It's just shuffling data around and using some C functions, all of which is pretty easy to do in Rust. With that said, I do agree that translating that code would be non-trivial for a Rust beginner and would require getting pretty comfy in the language first. You'd likely also have to redefine any structs that you need in Rust (or use a tool like `bindgen` to generate bindings to, e.g., netinet/udp.h for you). But still, as an experienced Rust programmer, I think that C example would be enough for me to tackle this particular problem. So this might just be a case of being unfamiliar with the language, which is totally fair. There are going to be far less resources for Rust when compared to C.
- nineteen999 7y ago
  Thanks for the advice regarding bindgen etc, I will look into that when I have more time. Generating the compatible structures (if Rust doesn't have them already) is one part of the problem, the other is really just the sendto() and socket() calls which as I mentioned are basically syscall wrappers for the most part. As per my other email, if I was writing this program in Rust, I'd prefer to use Rust all the way down rather then calling into C. Otherwise it's a Rust wrapper around C facilities. It should be possible do it all in native Rust code as far as I am concerned. As per my other message, I apologize if I have offended you, it certainly wasn't my intention, I was just trying to clarify the use of the raw IP API, as opposed to the higher level solution which wouldn't work for our simulator.
  - burntsushi 7y ago
    > It should be possible do it all in native Rust code as far as I am concerned. Yeah, it would be, but Rust's standard library doesn't provide any way to invoke syscalls. You either need to go through libc's syscall wrapper, or write Assembly. I used the former to get access to faster directory traversal: https://github.com/BurntSushi/walkdir/blob/ec33af7f9b25afefc3f37764b93fff132c3d54a6/src/os/linux/mod.rs#L41-L62 https://github.com/BurntSushi/walkdir/blob/ec33af7f9b25afefc... (The rest of that code in that module may be interesting to you, since the API for getdents is pretty interesting and very C-like. Buttoning it up behind a safe API that can never be misused took a bit of thinking.) Besides, Rust's standard library, on Linux at least, currently requires libc anyway. So you're already going to be linking to it.

woah 7y ago

The specific task is so obscure, that only a language as widespread as C would have an example online for it. So people are confused when you name this as a criteria for selecting a language, since it’s a criteria that most likely only C can satisfy. Then someone jumped to the conclusion that you were actually saying that Rust doesn’t have enough low level kernel APIs because that would make sense.

nineteen999 7y ago
> The specific task is so obscure, that only a language as widespread as C would have an example online for it. Well you could do it in Python I suppose - here's someone mentioning a solution using scapy, although it likely wouldn't work too well for my particular case due to Python performance. https://stackoverflow.com/questions/51311741/generating-a-spoofed-udp-packet-in-python https://stackoverflow.com/questions/51311741/generating-a-sp... > So people are confused when you name this as a criteria for selecting a language, since it’s a criteria that most likely only C can satisfy Rust is intended to be a replacement for C and C++, no? Eventually it will need to be able to do things like this if it is to be effective in that role. It's OK in my mind if it is not mature enough to do these kind of tasks yet, or if it can but I can't find a good reference yet. I wanted to use it for this task, but I selected C instead since it was easy to do that way and I didn't have a lot of time. Not holding it against Rust, it's a much younger language. > Then someone jumped to the conclusion that you were actually saying that Rust doesn’t have enough low level kernel APIs because that would make sense. I am almost completely certain I don't understand this sentence the way it is phrased.
- woah 7y ago
  Example code (for ARP though): https://github.com/libpnet/libpnet/blob/master/examples/arp_packet.rs https://github.com/libpnet/libpnet/blob/master/examples/arp_... Documentation: https://docs.rs/pnet/0.22.0/pnet/packet/udp/struct.MutableUdpPacket.html https://docs.rs/pnet/0.22.0/pnet/packet/udp/struct.MutableUd...
  - nineteen999 7y ago
    Thanks for this, those do look very helpful.
- rixed 7y ago
  In case you want to give OCaml a try one day, I've done plenty of stuff like that in the past when I needed a (much) faster scappy. UDP exemple here: https://github.com/rixed/robinet/blob/master/udp.ml https://github.com/rixed/robinet/blob/master/udp.ml
  - nineteen999 7y ago
    I'm not really a career programmer or language enthusiast, rather, I'm more of a utilitarian/imperative coder - I write programs to plug gaps in existing infrastructure as quickly, as securely, and as future-proofed as possible, even if it means dumbing the code down somewhat. So I think my head would explode if I tried to learn a FP language without being able to have months off work to study. In addition to that, my team would kill me, as it's hard enough to find good C/C++ programmers in my city, let alone something like OCaml. Given that we run emergency services infrastructure, unfortunately we have to use more popular languages to ensure that the business doesn't end up with a lot of code written in languages they can't support. Regardless, thank you very much for the example. It's nice to see that this can be done in other languages even if I can't understand it. Unfortunately too many years of C/C++ have made it hard for me to grok FP code - the C example I posted up before is much more readable to me.
    - ernst_klim 7y ago

burntsushi 7y ago

Yeah, I mean, as I mentioned, I hadn't done it before. I feel like I've put an appropriate amount of uncertainty in my comments, but I still feel like you're punishing me for it. In any case, I don't see anything particularly interesting in that C code. It's just shuffling data around and using some C functions, all of which is pretty easy to do in Rust. With that said, I do agree that translating that code would be non-trivial for a Rust beginner and would require getting pretty comfy in the language first. You'd likely also have to redefine any structs that you need in Rust (or use a tool like `bindgen` to generate bindings to, e.g., netinet/udp.h for you). But still, as an experienced Rust programmer, I think that C example would be enough for me to tackle this particular problem. So this might just be a case of being unfamiliar with the language, which is totally fair. There are going to be far less resources for Rust when compared to C.

nineteen999 7y ago
Thanks for the advice regarding bindgen etc, I will look into that when I have more time. Generating the compatible structures (if Rust doesn't have them already) is one part of the problem, the other is really just the sendto() and socket() calls which as I mentioned are basically syscall wrappers for the most part. As per my other email, if I was writing this program in Rust, I'd prefer to use Rust all the way down rather then calling into C. Otherwise it's a Rust wrapper around C facilities. It should be possible do it all in native Rust code as far as I am concerned. As per my other message, I apologize if I have offended you, it certainly wasn't my intention, I was just trying to clarify the use of the raw IP API, as opposed to the higher level solution which wouldn't work for our simulator.
- burntsushi 7y ago
  > It should be possible do it all in native Rust code as far as I am concerned. Yeah, it would be, but Rust's standard library doesn't provide any way to invoke syscalls. You either need to go through libc's syscall wrapper, or write Assembly. I used the former to get access to faster directory traversal: https://github.com/BurntSushi/walkdir/blob/ec33af7f9b25afefc3f37764b93fff132c3d54a6/src/os/linux/mod.rs#L41-L62 https://github.com/BurntSushi/walkdir/blob/ec33af7f9b25afefc... (The rest of that code in that module may be interesting to you, since the API for getdents is pretty interesting and very C-like. Buttoning it up behind a safe API that can never be misused took a bit of thinking.) Besides, Rust's standard library, on Linux at least, currently requires libc anyway. So you're already going to be linking to it.