RFC 1071 One's Complement Checksum in x64 Assembly: ICMP Carry Folding, Odd-Byte Handling & Packet Verification
ICMP packets with incorrect checksums are silently dropped by the kernel before reaching the destination. RFC 1071 mandates 16-bit one’s complement sum: accumulate packet words in eax, handle odd trailing byte separately, fold the carry bits (shr r11d,16 → and eax,0xFFFF → add ax,r11w → adc ax,0), invert with not ax. The receiver repeats the same sum — result must be 0xFFFF for a valid packet. Full x64 Assembly implementation with register layout, loop termination, and ICMP header integration.
