diff options
| -rw-r--r-- | networking/udhcp/d6_packet.c | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/networking/udhcp/d6_packet.c b/networking/udhcp/d6_packet.c index 3a1bb3df1..79b2946ef 100644 --- a/networking/udhcp/d6_packet.c +++ b/networking/udhcp/d6_packet.c @@ -92,16 +92,20 @@ int FAST_FUNC d6_send_raw_packet( /* size, excluding IP header: */ packet.udp.len = htons(sizeof(struct udphdr) + d6_pkt_size); packet.ip6.ip6_plen = packet.udp.len; - /* UDP checksum skips first four bytes of IP header. - * IPv6 'hop limit' field should be 0. - * 'next header' field should be summed as if it is in a different - * position, therefore we write its value into ip6_hlim: + /* + * Someone was smoking weed (at least) while inventing UDP checksumming: + * UDP checksum skips first four bytes of IPv6 header. + * 'next header' field should be summed as if it is one more byte + * to the right, therefore we write its value (IPPROTO_UDP) + * into ip6_hlim, and its 'real' location remains zero-filled for now. */ packet.ip6.ip6_hlim = IPPROTO_UDP; - packet.udp.check = inet_cksum((uint16_t *)&packet + 2, - offsetof(struct ip6_udp_d6_packet, data) - 4 + d6_pkt_size); + packet.udp.check = inet_cksum( + (uint16_t *)&packet + 2, + offsetof(struct ip6_udp_d6_packet, data) - 4 + d6_pkt_size + ); /* fix 'hop limit' and 'next header' after UDP checksumming */ - packet.ip6.ip6_hlim = 8; + packet.ip6.ip6_hlim = 1; /* observed Windows machines to use hlim=1 */ packet.ip6.ip6_nxt = IPPROTO_UDP; d6_dump_packet(d6_pkt); |