Text2pcap -n -e 0800 ipcks.txt ipcks.pcapng I understand this as indication that IPv4 is not supposed toĮxample to generate a PCAP with 0x0000 IPv4 header checksum and There are no mentioning to an additional inversion, if the resultingĪlso Wireshark shows an IPv4 header checksum error for packets withĬhecksum 0. > computing the checksum, the value of the checksum field is zero. > complement sum of all 16 bit words in the header. > The checksum field is the 16 bit one's complement of the one's However, the IPv4 header checksum is specified as: Return 0 by doing an additional inversion. The above function 'rte_ipv4_cksum()' is supposed to compute theĬhecksum of the /IPv4/ header and - like checksums for UDP - does not > debugging or for higher level protocols that don't care). > checksum value means that the transmitter generated no checksum (for > equivalent in one's complement arithmetic).
> If the computed checksum is zero, it is transmitted as all ones (the > data, padded with zero octets at the end (if necessary) to make a > pseudo header of information from the IP header, the UDP header, and the > Checksum is the 16-bit one's complement of the one's complement sum of a Therefore, a one's complement 16-bit sum "0xffff" is not inverted, whileĪll other values are (e.g. If the resulting value is 0, it is inverted again. Is computed from the one's complement sum of 16-bit words, followed by a In /UDP/, a checksum value 0x0000 means that no checksum was calculatedīy the sender and that the receiver cannot check anything. > return (cksum = 0xffff) ? cksum : ~cksum > cksum = rte_raw_cksum(ipv4_hdr, sizeof(struct ipv4_hdr)) > rte_ipv4_cksum(const struct ipv4_hdr *ipv4_hdr) I'm wondering whether I just failed to find the correct reference or if This is similar to the algorithm for UDPĬhecksums (where 0 is reserved for "no checksum"), but I could not findĪ reference that the same shall also be done for IPv4. The function for calculating the IPv4 header checksum avoids returning 0 Benes 0 siblings, 1 reply 2+ messages in thread Bug in IPv4 header checksum computation? DPDK usage discussions help / color / mirror / Atom feed * Bug in IPv4 header checksum computation? 15:03 N.
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