I was thinking the same thing. Which layer is responsible for this check? IP, UDP, or ICMP?
Στις Τρί 10 Μαΐ 2022 στις 2:41 μ.μ., ο/η Nathan Hartman < hartman.nat...@gmail.com> έγραψε: > On Tue, May 10, 2022 at 6:01 AM Fotis Panagiotopoulos <f.j.pa...@gmail.com > > > wrote: > > > Hello, > > > > I just noticed that NuttX responds with an ICMP port unreachable on UDP > > broadcasts. > > AFAIK this shouldn't happen. > > > > I followed the code, and I found that the broadcast reaches udp_input.c: > > line 256, where the ICMP response is generated. > > > > There is a note there that indeed the ICMP shouldn't be sent if this is a > > broadcast. > > As I see, the ICMP code is left to check this condition. > > > > Within icmp_reply.c: line 105 I see that there is a check about > broadcasts. > > My understanding is that this check is wrong. > > > > It checks for pure equality, between the destination IP and > > INADDR_BROADCAST. > > > > In my (quite typical) network, the broadcast IP is 192.168.1.255. > > The check expects to see exactly 255.255.255.255, so it fails to realise > > that this is a broadcast and responds nevertheless. > > > > Shall this check be fixed somehow? > > Or have I misunderstood something? > > > > Yes it is a good idea to fix it. > > Does this code know the netmask so as to check properly for all types of > broadcast addresses? E.g. with a netmask of 255.255.0.0 the broadcast > address is x.x.255.255. > > Nathan >
