Re: Problem with a UDP server implements
Hi! On 01:51 Sat 15 Oct , jiangtao.jit wrote: Hi: I'm writing a UDP server and meet a problem the UDP server program is run on a box with single card but has multi ip: likeeth010.0.0.1 eth0:1 10.0.0.2 eth0:2 11.0.0.1 I bind the server socket with INADDR_ANY ... when a client send a request to 10.0.0.1(eth0); the server use 10.0.0.1 to response and another client send a request to 10.0.0.2(eth0:1); the server use 10.0.0.2 to response Well, is seems there is neither a variant of recvfrom() which tells you your local address nor a variant of sendto() which allows you to specify your local address. I guess you have to call getaddrinfo() and create a socket for every address you want to bind to. If you want to stay single threaded you can switch them to nonblocking and use epoll to wait for packets. -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Problem with a UDP server implements
michi: 1. Is that to create two sockets and one bind to 10.0.0.1 the other bind to 10.0.0.2 then use epoll wait these two sockets ? 2. Is there any way to find out the turple like TCP then the UDP server can reply with exactly the ip it recieved the client's request ? Thanks. 2011/10/15 mic...@michaelblizek.twilightparadox.com: Hi! On 01:51 Sat 15 Oct , jiangtao.jit wrote: Hi: I'm writing a UDP server and meet a problem the UDP server program is run on a box with single card but has multi ip: like eth0 10.0.0.1 eth0:1 10.0.0.2 eth0:2 11.0.0.1 I bind the server socket with INADDR_ANY ... when a client send a request to 10.0.0.1(eth0); the server use 10.0.0.1 to response and another client send a request to 10.0.0.2(eth0:1); the server use 10.0.0.2 to response Well, is seems there is neither a variant of recvfrom() which tells you your local address nor a variant of sendto() which allows you to specify your local address. I guess you have to call getaddrinfo() and create a socket for every address you want to bind to. If you want to stay single threaded you can switch them to nonblocking and use epoll to wait for packets. -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Getting 'bad file number' error writing to device driver
On Sat, Oct 15, 2011 at 2:42 AM, Philip Anil-QBW348 anil.phi...@motorolasolutions.com wrote: I am calling the driver from an Android program (OMAP4/Blaze). It calls a c++ program via JNI which then calls the device driver. Someone suggested it might be a permissions problem - the program is running in user mode. on Blaze board, /system/bin # ls -l -rwxrwxrwx system system 7636 2011-09-30 03:53 mydriver Will strace still be useful? In general, in Linux, how does one enable a user program to call a custom device driver? Please don't top post! :) strace will be useful to check the parameters for open, write system calls. EBADF fd is not a valid file descriptor or is not open for writing. Ok, so either open fails, or you don't have the permission to write into /dev/mydriver file. Another thing that I can think of, is that your driver's write function is wrong, and returns -EBADF in some case ? Can you give us a pointer to your driver? thanks, Daniel. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Problem with a UDP server implements
michi: Thanks for your help. Much appreciated. 2011/10/15 mic...@michaelblizek.twilightparadox.com: Hi! On 16:29 Sat 15 Oct , tao jiang wrote: michi: 1. Is that to create two sockets and one bind to 10.0.0.1 the other bind to 10.0.0.2 then use epoll wait these two sockets ? Yes, exactly. 2. Is there any way to find out the turple like TCP then the UDP server can reply with exactly the ip it recieved the client's request ? You should receive the packet only on the socket which is bound to the address. You can save the bind address somewhere, so you know the local address. You will know the client address because it is passed back by recvfrom. -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Query on Rx Frame processing
I'm trying to understand Linux Network subsystem and after reading some documents, my broad level understanding for Rx Path is as follows: 1: Card receives the packet. 2: Assume everything is fine, the card DMAs the frame for the driver to process it further. 3: Driver allocate an skb buffer, adjusts the headroom. 4: Fills the buffer and pass it to the Network layer. Now in step 4 above, driver passes this packet to the network layer by calling netif_receive_skb() which may return NET_RX_DROP (packet was dropped), but most (I checked some of the network driver code) of the network drivers do not do this check. Hence, Q1: Shouldn't drivers be doing that ? Q2: Suppose the Card keeps pushing the frames at very high rate (10 Gig adapters are already in the market and maybe in near future we might have even faster ethernet adapters) then how the driver and the networking stack will handle such rapid frames arrivals? Will NAPI, interrupt coalescing be enough ? I'm referring kernel version 2.6.31 -Amit ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Query on Rx Frame processing
Hi! On 19:45 Sat 15 Oct , amit mehta wrote: ... Now in step 4 above, driver passes this packet to the network layer by calling netif_receive_skb() which may return NET_RX_DROP (packet was dropped), but most (I checked some of the network driver code) of the network drivers do not do this check. Hence, Q1: Shouldn't drivers be doing that ? The return value NET_RX_DROP seems to be used in various places where no congestion exists: http://lxr.linux.no/linux+v3.0.4/net/ipv4/ip_forward.c#L131 http://lxr.linux.no/linux+v3.0.4/net/ipv4/ip_input.c#L369 http://lxr.linux.no/linux+v3.0.4/net/ipv4/ip_input.c#L451 What should network drivers do with this info? Also, there might be multiple layer 3 protocols. If one of them would signal congestion, should the driver slow down receiving? Maybe the question is rather why does this variable exist at all. I guess it is just to got statistic data. Q2: Suppose the Card keeps pushing the frames at very high rate (10 Gig adapters are already in the market and maybe in near future we might have even faster ethernet adapters) then how the driver and the networking stack will handle such rapid frames arrivals? Will NAPI, interrupt coalescing be enough ? It seems like net_rx_action does some throttling: http://lxr.linux.no/linux+v3.0.4/net/core/dev.c#L3764 -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Heap memory is not re-claiming.
On Fri, Oct 14, 2011 at 10:28 AM, rohan puri rohan.pur...@gmail.com wrote: *Reference to an article by Mulayadi Santosa :- http://linuxdevcenter.com/pub/a/linux/2006/11/30/linux-out-of-memory.html * Rohan, thanks a lot for sharing this link. Mulyadi, the article is just superb, very well-written and extremely useful :) Regards, Srivatsa S. Bhat ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
