This drove me nuts this morning and i find it hard to believe that no-one has reported this before because i went back as far back as 2.4.2 and it is there ;->. I am ccing the three people who may possibly have made this change (no records whatsoever in git);->
When you turn off ARP on a netdevice then the first packet always goes out with a dstMAC of all zeroes. This is because the first packet is used to resolve ARP entries. Even though the ARP entry may be resolved (I tried by setting a static ARP entry for a host i was pinging from), it gets overwritten by virtue of having the netdevice disabling ARP. Subsequent packets go out fine with correct dstMAC address (which may be why people have ignored reporting this issue). To cut the story short: the culprit code is in net/ethernet/eth.c::eth_header() ---- /* * Anyway, the loopback-device should never use this function... */ if (dev->flags & (IFF_LOOPBACK|IFF_NOARP)) { memset(eth->h_dest, 0, dev->addr_len); return ETH_HLEN; } if(daddr) { memcpy(eth->h_dest,daddr,dev->addr_len); return ETH_HLEN; } ---- Note how the h_dest is being reset when device has IFF_NOARP. The only reason i am asking is that this small piece of code has some huge impact and i dont understand the history of IFF_NOARP check being put there. As a note: All devices including loopback pass a daddr. loopback in fact passes a 0 all the time ;-> This means i can delete the check totaly or i can remove the IFF_NOARP Anyone knows the history? cheers, jamal - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html