Anyone knows if the maximum number of file descriptors that can be passed  
via SCM_RIGHTS is documented anywhere?

Up to at least 2.6.35, I could stuff as many as 255 file descriptors. Which  
sort of made sense.

I updated to Fedora 15, which is based on 2.6.38, and the maximum number of  
file descriptors I can stuff into a message seems to be 253. With 254,  
strace tells me that the kernel refuses with EINVAL.