generating ECONNRESET with no syscall?

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

Is it, for a user process, legally possible to put one of its socket into a 
state where trying to connect to it returns ECONNRESET without the process 
issuing any syscalls during the connection attempt?

We have two production web servers, both running lighttpd, the first still 
running on NetBSD 4.0.1, the second on 6.1. Occasioally, on the second, you 
get Connection Reset by Peer (NOT Connection Refused) on the HTTP port. 
ktrace-ng the lighttpd process reveals close to no activity. Restarting 
lighttpd instantly resolves the problem. Is there any way the lighttpd process 
may have put its socket into this condition or must this be a kernel issue?