Thanks John for ur immediate response. The code you have given will set the interface specified (thru parameter d) to promisc mode. My question was something else. There are few differences though between the code given by you and what I am trying to do. 1. I am using "socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)" for listening on Ethernet directly. 2. recvfrom() api receives all the packets destined to my machine (ie. on all the NICs supported). My concern was that there could be packet loss when i have one recvfrom() to capture packets on all the NICs. So wanted to have a separate process to listen on each NIC. For this purpose, I was looking for a way where in I could specify to receive packets only from a single NIC (say eth2) and not from others. I think, i have got a solution for this now. Before i call recvfrom (), I am binding the socket (packet socket) to the interface from where i want to receive the packets and this does the trick. But will this solve my original purpose of reducing packet loss? Re, Chuks -----Original Message----- From: Evgeniy Polyakov [mailto:johnpol@2ka.mipt.ru] Sent: Wednesday, November 28, 2001 6:18 PM To: chakraa@future.futsoft.com Cc: linux-net@vger.kernel.org Subject: Re: Sniffing on a specific NIC On Wed, 28 Nov 2001 17:49:54 +0530 "chakri" <chakraa@future.futsoft.com> wrote: > Hi, > > I have a machine with multiple NICs supported. > I am trying to capture packets using the PACKET_SOCKET directly on the > Ethernet. > It is observed that recvfrom () captures packets received on all the NICs > supported in the host. > I do have a mechanism of sorting the packets based on NIC (using sa_addr > member of sockaddr structure). But how do I capture only those packets > coming on a specific NIC (say eth1). Is there a way wherein I specify to > receive packets coming at a particular interface only? int openintf(char *d) { int fd; struct ifreq ifr; int s; fd=socket(AF_INET, SOCK_PACKET, htons(0x800)); if(fd < 0) { perror("cant get SOCK_PACKET socket"); exit(0); } strcpy(ifr.ifr_name, d); s=ioctl(fd, SIOCGIFFLAGS, &ifr); if(s < 0) { close(fd); perror("cant get flags"); exit(0); } ifr.ifr_flags |= IFF_PROMISC; s= ioctl(fd, SIOCSIFFLAGS, &ifr); if(s < 0) perror("cant set promiscuous mode"); return fd; } May be it is what you want? Parameter for openintf() must be the name of an interface to open, t.e. for example "eth1". And after it you can read()/write() from/to obtained socket. > > Re, > Chuks --- WBR. //s0mbre - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
