fix tcp:kernel::debug-input trace: the given tcphdr (args[1]) is already partially in host order (namely seq, ack, window size, urgent pointer)

[hannes_mehnert.org]

Summary

tcp.d provides both tcpinfo_t and tcpinfoh_t - where the former is for tcphdr structs in network order, and the latter for tcphdr which are partially in host order.
now, debug__input is used in tcp_input and tcp_do_segment, but only after tcp_fields_to_host(th) (in line 766) was called.

Sponsored by: REMS (rems.io)

Test Plan

start a tcpdump (to see the sequence number of a session) and run the following D program at the same time:

tcp:kernel::debug-input {
    printf("seq %u\n", args[1]->tcp_seq);
}

before this patch (on a little endian machine), you'll see the wrong sequence number. after, it is the one you expected (and the same as in tcpdump)

[hannes_mehnert.org]

debug__drop as well uses a partially host-order converted tcphdr

after checking, same applies to debug__drop (only used in tcp_stacks/fastpath.c). debug__output is fine as is

[markj]

Thanks, this seems right to me.