I’m learning to use raw sockets, and im trying to prase out the tcp

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Asked: May 14, 20262026-05-14T00:54:40+00:00 2026-05-14T00:54:40+00:00

I’m learning to use raw sockets, and im trying to prase out the tcp

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I’m learning to use raw sockets, and im trying to prase out the tcp header data, but i can’t seem to figure out what res1, ece, and cwr are. Through my networking book and google i know what the rest stand for, but can’t seem to find anything on those three.
Below is the tcphdr struct in my includes area. Ive commented the parts a bit as i was figureing out what they stood for.

struct tcphdr {
        __be16  source;
        __be16  dest;
        __be32  seq;
        __be32  ack_seq;
\#if defined(__LITTLE_ENDIAN_BITFIELD)
        __u16   res1:4,
                doff:4,//tcp header length
                fin:1,//final
                syn:1,//synchronization
                rst:1,//reset
                psh:1,//push
                ack:1,//ack
                urg:1,// urge
                ece:1,
                cwr:1;
\#elif defined(__BIG_ENDIAN_BITFIELD)
        __u16   doff:4,//tcp header length
                res1:4,
                cwr:1,
                ece:1,
                urg:1,//urge
                ack:1,//ack
                psh:1,//push
                rst:1,//reset
                syn:1,//synchronization
                fin:1;//final
\#else
\#error  "Adjust your <asm/byteorder.h> defines"
\#endif
        __be16  window;
        __sum16 check;
        __be16  urg_ptr;
};