| Message ID | 3ca0fe4de1f701befbc874e4b672c90aee602199.1674752051.git.petrm@nvidia.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | bridge: Limit number of MDB entries per port, port-vlan | expand |
On 26/01/2023 19:01, Petr Machata wrote: > In order to generate IGMPv3 and MLDv2 packets on the fly, we will need > helpers to calculate the packet checksum. > > The approach presented in this patch revolves around payload templates > for mausezahn. These are mausezahn-like payload strings (01:23:45:...) > with possibly one 2-byte sequence replaced with the word PAYLOAD. The > main function is payload_template_calc_checksum(), which calculates > RFC 1071 checksum of the message. There are further helpers to then > convert the checksum to the payload format, and to expand it. > > For IPv6, MLDv2 message checksum is computed using a pseudoheader that > differs from the header used in the payload itself. The fact that the > two messages are different means that the checksum needs to be > returned as a separate quantity, instead of being expanded in-place in > the payload itself. Furthermore, the pseudoheader includes a length of > the message. Much like the checksum, this needs to be expanded in > mausezahn format. And likewise for number of addresses for (S,G) > entries. Thus we have several places where a computed quantity needs > to be presented in the payload format. Add a helper u16_to_bytes(), > which will be used in all these cases. > > Signed-off-by: Petr Machata <petrm@nvidia.com> > --- > tools/testing/selftests/net/forwarding/lib.sh | 56 +++++++++++++++++++ > 1 file changed, 56 insertions(+) > Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
diff --git a/tools/testing/selftests/net/forwarding/lib.sh b/tools/testing/selftests/net/forwarding/lib.sh index 8f7e2cc8b779..1c5ca7552881 100755 --- a/tools/testing/selftests/net/forwarding/lib.sh +++ b/tools/testing/selftests/net/forwarding/lib.sh @@ -1730,6 +1730,62 @@ ipv6_to_bytes() expand_ipv6 "$IP" : } +u16_to_bytes() +{ + local u16=$1; shift + + printf "%04x" $u16 | sed 's/^/000/;s/^.*\(..\)\(..\)$/\1:\2/' +} + +# Given a mausezahn-formatted payload (colon-separated bytes given as %#02x), +# possibly with a keyword CHECKSUM stashed where a 16-bit checksum should be, +# calculate checksum as per RFC 1071, assuming the CHECKSUM field (if any) +# stands for 00:00. +payload_template_calc_checksum() +{ + local payload=$1; shift + + ( + # Set input radix. + echo "16i" + # Push zero for the initial checksum. + echo 0 + + # Pad the payload with a terminating 00: in case we get an odd + # number of bytes. + echo "${payload%:}:00:" | + sed 's/CHECKSUM/00:00/g' | + tr '[:lower:]' '[:upper:]' | + # Add the word to the checksum. + sed 's/\(..\):\(..\):/\1\2+\n/g' | + # Strip the extra odd byte we pushed if left unconverted. + sed 's/\(..\):$//' + + echo "10000 ~ +" # Calculate and add carry. + echo "FFFF r - p" # Bit-flip and print. + ) | + dc | + tr '[:upper:]' '[:lower:]' +} + +payload_template_expand_checksum() +{ + local payload=$1; shift + local checksum=$1; shift + + local ckbytes=$(u16_to_bytes $checksum) + + echo "$payload" | sed "s/CHECKSUM/$ckbytes/g" +} + +payload_template_nbytes() +{ + local payload=$1; shift + + payload_template_expand_checksum "${payload%:}" 0 | + sed 's/:/\n/g' | wc -l +} + igmpv3_is_in_get() { local igmpv3
In order to generate IGMPv3 and MLDv2 packets on the fly, we will need helpers to calculate the packet checksum. The approach presented in this patch revolves around payload templates for mausezahn. These are mausezahn-like payload strings (01:23:45:...) with possibly one 2-byte sequence replaced with the word PAYLOAD. The main function is payload_template_calc_checksum(), which calculates RFC 1071 checksum of the message. There are further helpers to then convert the checksum to the payload format, and to expand it. For IPv6, MLDv2 message checksum is computed using a pseudoheader that differs from the header used in the payload itself. The fact that the two messages are different means that the checksum needs to be returned as a separate quantity, instead of being expanded in-place in the payload itself. Furthermore, the pseudoheader includes a length of the message. Much like the checksum, this needs to be expanded in mausezahn format. And likewise for number of addresses for (S,G) entries. Thus we have several places where a computed quantity needs to be presented in the payload format. Add a helper u16_to_bytes(), which will be used in all these cases. Signed-off-by: Petr Machata <petrm@nvidia.com> --- tools/testing/selftests/net/forwarding/lib.sh | 56 +++++++++++++++++++ 1 file changed, 56 insertions(+)