panic: kernel diagnostic assertion "ifp != NULL" failed: file "/syzkaller/managers/main/kernel/sys/net/rtsock.c", line 939
Stopped at      db_enter+0x18:  addq    $0x8,%rsp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*412212   4691      0           0  0x4000000    0  syz-executor.1
db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398
panic(ffffffff823c20ed) at panic+0x15c sys/kern/subr_prf.c:207
__assert(ffffffff8242d39c,ffffffff823dae3b,3ab,ffffffff8239a6b1) at __assert+0x2b sys/kern/subr_prf.c:154
rtm_output(ffff800000ae1c00,ffff8000207b3bb0,ffff8000207b3b08,40,0) at rtm_output+0xba9 sys/net/rtsock.c:1120
route_output(fffffd800604e200,fffffd80539901a8,0,0) at route_output+0x678 sys/net/rtsock.c:832
route_usrreq(fffffd80539901a8,9,fffffd800604e200,0,0,ffff80001d6c14f8) at route_usrreq+0x36f sys/net/rtsock.c:275
sosend(fffffd80539901a8,0,ffff8000207b3da0,0,0,0) at sosend+0x669 sys/kern/uipc_socket.c:549
sendit(ffff80001d6c14f8,3,ffff8000207b3e80,0,ffff8000207b3f60) at sendit+0x52b sys/kern/uipc_syscalls.c:652
sys_sendto(ffff80001d6c14f8,ffff8000207b3f18,ffff8000207b3f60) at sys_sendto+0x80 sys/kern/uipc_syscalls.c:517
syscall(ffff8000207b3fe0) at syscall+0x507 sys/arch/amd64/amd64/trap.c:570
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x5848da1c1a0, count: 4
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports.  Insufficient info makes it difficult to find and fix bugs.