On Sun, 11 Jan 2015 at 0:27:06 +0000, Al Viro wrote: > On Sat, Jan 10, 2015 at 11:25:18PM +0000, Carlos R. Mafra wrote: > > [mafra@linux-g29b:wmnet]$ cat net_dev_bad.txt > > Inter-| Receive | Transmit > > face |bytes packets errs drop fifo frame compressed multicast|bytes > > packets errs drop fifo colls carrier compressed > > lo: 600 8 0 0 0 0 0 0 600 > > 8 0 0 0 0 0 0 > > wlp3s0b1: 9266848 7298 0 0 0 0 0 0 > > 372229 4030 0 0 0 0 0 0 > > > > And for some reason this change confuses 'wmnet'. Reading the source code > > of 'wmnet' I found that it reads the packets as follows, > > > > totalpackets_in = strtoul(&buffer[15], NULL, 10); > > > > I am not sure if 'wmnet' could do this better (any suggestions?), > > *snort* > > well, yes - it's called scanf(). And if one is really, really nervous > about the overhead of <gasp> parsing a bunch of integers (as if fopen/ > fgets/fclose alone won't cost enough to make constantly calling that > sucker a bad idea), just use ptr + <something> - 6 instead of > &buffer[<something>] in there. That thing has just found where the > colon was (and replaced it with NUL), so dealing with "the first field > turned out to be too long and shifted everything past it" isn't hard.
Alright! Thank you. > > but the fact is that it was working before and now it is not. > > True. Mind you, the real issue is that this code expects the interface > names to be never longer than 6 characters, but then /proc/net/dev layout > strongly suggests that. Hell knows; it is a regression and it does > break real-world userland code. The only way to avoid that, AFAICS, is > to prohibit interface names longer than 6 chars ;-/ > > Lovely combination of crappy ABI (procfs file layout), crappy userland > code relying on details of said ABI out of sheer laziness and triggering > kernel change producing bloody long interface names... I won't mind just changing the crappy and fragile wmnet code and moving on. I have already lost the 2 hours bisecting this anyway. Thank you very much for your advice. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
