In tcp_output, change len from platform-dependent long to fixed-length int32_t.
You're going to see this in several of my reviews. The "right thing" (TM) to do is to use the PRId32 macro. But, I didn't want to do that, since we don't use it anywhere else in the kernel code.
But, thinking through this more, an int format specifier should work for this. We don't have platforms with ints less than 32 bits, and aren't likely to get one in the future. I'll get all those reviews updated and resubmit.