raw-sockets

问题 I like to know the source port of packet in tcphdr can be assigned to destination port of ip like this source_ip_tcph->source= dest_ip_tcph->dest; source_ip_tcph->dest = dest_ip_tcph->source; above are source and destination (pointer to memory) of tcphdr type I am trying to create a server everytime I respond to client from server the destination port is different. I assigned it like above Edit Above I am using raw sockets. trying to make raw socket based tcp implementation as a server 来源：

问题 I like to know the source port of packet in tcphdr can be assigned to destination port of ip like this source_ip_tcph->source= dest_ip_tcph->dest; source_ip_tcph->dest = dest_ip_tcph->source; above are source and destination (pointer to memory) of tcphdr type I am trying to create a server everytime I respond to client from server the destination port is different. I assigned it like above Edit Above I am using raw sockets. trying to make raw socket based tcp implementation as a server 来源：

问题 I like to know the source port of packet in tcphdr can be assigned to destination port of ip like this source_ip_tcph->source= dest_ip_tcph->dest; source_ip_tcph->dest = dest_ip_tcph->source; above are source and destination (pointer to memory) of tcphdr type I am trying to create a server everytime I respond to client from server the destination port is different. I assigned it like above Edit Above I am using raw sockets. trying to make raw socket based tcp implementation as a server 来源：

问题 sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &f, sizeof (f)) With this simple BPF/LPF attach code, when I try to receive packet on the socket, will get some wrong packets that doesn't match with the filter. Seems those packets got into the socket before I call setsockopt(). Seems like should first create the AF_PACKET SOCK_RAW socket, then attach the filter, then flush the socket to get rid of those wrong packets. So the question is, how

问题 sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &f, sizeof (f)) With this simple BPF/LPF attach code, when I try to receive packet on the socket, will get some wrong packets that doesn't match with the filter. Seems those packets got into the socket before I call setsockopt(). Seems like should first create the AF_PACKET SOCK_RAW socket, then attach the filter, then flush the socket to get rid of those wrong packets. So the question is, how

问题 My question has roughly been discussed here. And the tl;dr solution is to do: iptables -A OUTPUT -p tcp --tcp-flags RST RST -j DROP And you could modify this to only block the port you're actively listening after. But as mentioned in the above question, and here, these are not elegant solutions. Now, I don't really care about the elegance of things. But I do care about learning. So I've dug deep into the Linux source code (mostly interested in Linux based machines for now) and sorted through

问题 I am trying to initiate a TCP Three-Way-Handshake in C. However, it occurred to me that connect may already be establishing such a connection or in some way interfering. Does connect automatically establish a TCP connection whenever the socket it's called on has the IPPROTO_TCP option set? 回答1: Yes, IPPROTO_TCP creates TCP socket. To use raw socket, you need to pass SOCK_RAW as second argument to the socket function. 回答2: Per MSDN documentation: TCP/IP Raw Sockets Once an application creates

问题 I am trying to initiate a TCP Three-Way-Handshake in C. However, it occurred to me that connect may already be establishing such a connection or in some way interfering. Does connect automatically establish a TCP connection whenever the socket it's called on has the IPPROTO_TCP option set? 回答1: Yes, IPPROTO_TCP creates TCP socket. To use raw socket, you need to pass SOCK_RAW as second argument to the socket function. 回答2: Per MSDN documentation: TCP/IP Raw Sockets Once an application creates

问题 I am trying to write an application to sniff traffic being sent to an ethernet port on my server. My application never needs to send data. It only needs to receive and decode the 5-tuple. I am opening the socket with: socket (AF_INET, SOCK_RAW, htons (ETH_P_ALL)) and setting it to promiscuous mode: struct ifreq ifr; ioctl (raw_socket, SIOCGIFFLAGS, &ifr); /* Set the old flags plus the IFF_PROMISC flag */ ifr.ifr_flags |= IFF_PROMISC; ioctl (raw_socket, SIOCSIFFLAGS, &ifr); I am using recv to

问题 When capturing network traffic for debugging, there seem to be two common approaches: Use a raw socket. Use libpcap. Performance-wise, is there much difference between these two approaches? libpcap seems a nice compatible way to listen to a real network connection or to replay some canned data, but does that feature set come with a performance hit? 回答1: The answer is intended to explain more about the libpcap. libpcap uses the PF_PACKET to capture packets on an interface. Refer to the