current kern.ipc.maxsockbuf = 524288 (sysctl ok=1)
write #1: 8-byte value 0x0000000100001000 -> sysctl returned 0 (ok)
after 8-byte write of 0x100001000, sb_max = 4096 (0x1000)  <-- low 32 bits kept, high half silently dropped
write #2: 8-byte 0x100080000 -> ret=0, sb_max = 524288 (0x80000)  <-- became 0x80000, magnitude wrong by 4 GiB
restored: sb_max = 524288 (ret=0)