Re: [PATCH v4 1/2] net: add functions to calculate UDP/TCP cksum in mbuf

["Singh, Aman Deep" <aman.deep.singh@intel.com>]

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On 1/4/2022 9:10 PM, Li, Xiaoyun wrote:
> Hi
>
>> -----Original Message-----
>> From: Li, Xiaoyun<xiaoyun.li@intel.com>
>> Sent: Tuesday, January 4, 2022 15:19
>> To: Singh, Aman Deep<aman.deep.singh@intel.com>; Yigit, Ferruh
>> <ferruh.yigit@intel.com>;olivier.matz@6wind.com;
>> mb@smartsharesystems.com; Ananyev, Konstantin
>> <konstantin.ananyev@intel.com>;stephen@networkplumber.org;
>> Medvedkin, Vladimir<vladimir.medvedkin@intel.com>
>> Cc:dev@dpdk.org
>> Subject: RE: [PATCH v4 1/2] net: add functions to calculate UDP/TCP cksum in
>> mbuf
>>
>> Hi
>>
>>> -----Original Message-----
>>> From: Singh, Aman Deep<aman.deep.singh@intel.com>
>>> Sent: Wednesday, December 15, 2021 11:34
>>> To: Li, Xiaoyun<xiaoyun.li@intel.com>; Yigit, Ferruh
>>> <ferruh.yigit@intel.com>;olivier.matz@6wind.com;
>>> mb@smartsharesystems.com; Ananyev, Konstantin
>>> <konstantin.ananyev@intel.com>;stephen@networkplumber.org;
>> Medvedkin,
>>> Vladimir<vladimir.medvedkin@intel.com>
>>> Cc:dev@dpdk.org
>>> Subject: Re: [PATCH v4 1/2] net: add functions to calculate UDP/TCP
>>> cksum in mbuf
>>>
>>>
>>> On 12/3/2021 5:08 PM, Xiaoyun Li wrote:
>>>> Add functions to call rte_raw_cksum_mbuf() to calculate IPv4/6
>>>> UDP/TCP checksum in mbuf which can be over multi-segments.
>>>>
>>>> Signed-off-by: Xiaoyun Li<xiaoyun.li@intel.com>

Acked-by: Aman Singh <aman.deep.singh@intel.com>

>>>> ---
>>>>    doc/guides/rel_notes/release_22_03.rst |  10 ++
>>>>    lib/net/rte_ip.h                       | 186 +++++++++++++++++++++++++
>>>>    lib/net/version.map                    |  10 ++
>>>>    3 files changed, 206 insertions(+)
>>>>
>>>> diff --git a/doc/guides/rel_notes/release_22_03.rst
>>>> b/doc/guides/rel_notes/release_22_03.rst
>>>> index 6d99d1eaa9..7a082c4427 100644
>>>> --- a/doc/guides/rel_notes/release_22_03.rst
>>>> +++ b/doc/guides/rel_notes/release_22_03.rst
>>>> @@ -55,6 +55,13 @@ New Features
>>>>         Also, make sure to start the actual text at the margin.
>>>>         =======================================================
>>>>
>>>> +* **Added functions to calculate UDP/TCP checksum in mbuf.**
>>>> +  * Added the following functions to calculate UDP/TCP checksum of
>>> packets
>>>> +    which can be over multi-segments:
>>>> +    - ``rte_ipv4_udptcp_cksum_mbuf()``
>>>> +    - ``rte_ipv4_udptcp_cksum_mbuf_verify()``
>>>> +    - ``rte_ipv6_udptcp_cksum_mbuf()``
>>>> +    - ``rte_ipv6_udptcp_cksum_mbuf_verify()``
>>>>
>>>>    Removed Items
>>>>    -------------
>>>> @@ -84,6 +91,9 @@ API Changes
>>>>       Also, make sure to start the actual text at the margin.
>>>>       =======================================================
>>>>
>>>> +* net: added experimental functions
>>>> +``rte_ipv4_udptcp_cksum_mbuf()``,
>>>> +  ``rte_ipv4_udptcp_cksum_mbuf_verify()``,
>>>> +``rte_ipv6_udptcp_cksum_mbuf()``,
>>>> +  ``rte_ipv6_udptcp_cksum_mbuf_verify()``
>>>>
>>>>    ABI Changes
>>>>    -----------
>>>> diff --git a/lib/net/rte_ip.h b/lib/net/rte_ip.h index
>>>> c575250852..534f401d26 100644
>>>> --- a/lib/net/rte_ip.h
>>>> +++ b/lib/net/rte_ip.h
>>>> @@ -400,6 +400,65 @@ rte_ipv4_udptcp_cksum(const struct
>> rte_ipv4_hdr
>>> *ipv4_hdr, const void *l4_hdr)
>>>>    	return cksum;
>>>>    }
>>>>
>>>> +/**
>>>> + * @internal Calculate the non-complemented IPv4 L4 checksum of a
>>>> +packet  */ static inline uint16_t
>>>> +__rte_ipv4_udptcp_cksum_mbuf(const
>>>> +struct rte_mbuf *m,
>>>> +			     const struct rte_ipv4_hdr *ipv4_hdr,
>>>> +			     uint16_t l4_off)
>>>> +{
>>>> +	uint16_t raw_cksum;
>>>> +	uint32_t cksum;
>>>> +
>>>> +	if (l4_off > m->pkt_len)
>>>> +		return 0;
>>>> +
>>>> +	if (rte_raw_cksum_mbuf(m, l4_off, m->pkt_len - l4_off,
>>> &raw_cksum))
>>>> +		return 0;
>>>> +
>>>> +	cksum = raw_cksum + rte_ipv4_phdr_cksum(ipv4_hdr, 0);
>>>> +
>>>> +	cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff);
>>> At times, even after above operation "cksum" might stay above 16-bits,
>>> ex "cksum = 0x1FFFF" to start with.
>>> Can we consider using "return __rte_raw_cksum_reduce(cksum);"
>> Will use it in next version. Thanks.
>>
>> Also, not related to this patch. It means that __rte_ipv4_udptcp_cksum and
>> __rte_ipv6_udptcp_cksum have the same issue, right?
>> Should anyone fix that?
> Forgot the intent here.
> rte_raw_cksum_mbuf() already calls __rte_raw_cksum_reduce().
> So actually, it's a result of uint16_t + uint16_t. So it's impossible of your case. There's no need to call __rte_raw_cksum_reduce().
Got it, Thanks. With u16 + u16, max 1-bit overflow only possible. So 
effective operation here reduces to-

cksum = ((cksum & 0x10000) >> 16) + (cksum & 0xffff);

>>>> +
>>>> +	return (uint16_t)cksum;
>>>> +}
>>>> +
>>>> +/**
>>>> + * @warning
>>>> + * @b EXPERIMENTAL: this API may change without prior notice.
>>>> + *
>>>> + * Compute the IPv4 UDP/TCP checksum of a packet.
>>>> + *
>>>> + * @param m
>>>> + *   The pointer to the mbuf.
>>>> + * @param ipv4_hdr
>>>> + *   The pointer to the contiguous IPv4 header.
>>>> + * @param l4_off
>>>> + *   The offset in bytes to start L4 checksum.
>>>> + * @return
>>>> + *   The complemented checksum to set in the L4 header.
>>>> + */
>>>> +__rte_experimental
>>>> +static inline uint16_t
>>>> +rte_ipv4_udptcp_cksum_mbuf(const struct rte_mbuf *m,
>>>> +			   const struct rte_ipv4_hdr *ipv4_hdr, uint16_t l4_off)
>>> {
>>>> +	uint16_t cksum = __rte_ipv4_udptcp_cksum_mbuf(m, ipv4_hdr,
>>> l4_off);
>>>> +
>>>> +	cksum = ~cksum;
>>>> +
>>>> +	/*
>>>> +	 * Per RFC 768: If the computed checksum is zero for UDP,
>>>> +	 * it is transmitted as all ones
>>>> +	 * (the equivalent in one's complement arithmetic).
>>>> +	 */
>>>> +	if (cksum == 0 && ipv4_hdr->next_proto_id == IPPROTO_UDP)
>>>> +		cksum = 0xffff;
>>>> +
>>>> +	return cksum;
>>>> +}
>>>> +
>>>>    /**
>>>>     * Validate the IPv4 UDP or TCP checksum.
>>>>     *
>>>> @@ -426,6 +485,38 @@ rte_ipv4_udptcp_cksum_verify(const struct
>>> rte_ipv4_hdr *ipv4_hdr,
>>>>    	return 0;
>>>>    }
>>>>
>>>> +/**
>>>> + * @warning
>>>> + * @b EXPERIMENTAL: this API may change without prior notice.
>>>> + *
>>>> + * Verify the IPv4 UDP/TCP checksum of a packet.
>>>> + *
>>>> + * In case of UDP, the caller must first check if
>>>> +udp_hdr->dgram_cksum is 0
>>>> + * (i.e. no checksum).
>>>> + *
>>>> + * @param m
>>>> + *   The pointer to the mbuf.
>>>> + * @param ipv4_hdr
>>>> + *   The pointer to the contiguous IPv4 header.
>>>> + * @param l4_off
>>>> + *   The offset in bytes to start L4 checksum.
>>>> + * @return
>>>> + *   Return 0 if the checksum is correct, else -1.
>>>> + */
>>>> +__rte_experimental
>>>> +static inline uint16_t
>>>> +rte_ipv4_udptcp_cksum_mbuf_verify(const struct rte_mbuf *m,
>>>> +				  const struct rte_ipv4_hdr *ipv4_hdr,
>>>> +				  uint16_t l4_off)
>>>> +{
>>>> +	uint16_t cksum = __rte_ipv4_udptcp_cksum_mbuf(m, ipv4_hdr,
>>> l4_off);
>>>> +
>>>> +	if (cksum != 0xffff)
>>>> +		return -1;
>>> cksum other than 0xffff, should return error. Is that the intent or I
>>> am missing something obvious.
>> This is the intent. This function is to verify if the cksum in the packet is correct.
>>
>> It's different from calling rte_ipv4/6_udptcp_cksum_mbuf(). When calling
>> rte_ipv4/6_udptcp_cksum_mbuf(), you need to set the cksum in udp/tcp
>> header as 0. Then calculate the cksum.
>>
>> But here, user should directly call this function with the original packet. Then
>> if the udp/tcp cksum is correct, after the calculation (please note that, this is
>> calling __rte_ipv4_udptcp_cksum_mbuf(), so the result needs to be ~), it
>> should be 0xffff, namely, ~cksum = 0 which means cksum is correct. You can
>> see rte_ipv4/6_udptcp_cksum_verify() is doing the same.
>>
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>>    /**
>>>>     * IPv6 Header
>>>>     */
>>>> @@ -538,6 +629,68 @@ rte_ipv6_udptcp_cksum(const struct
>> rte_ipv6_hdr
>>> *ipv6_hdr, const void *l4_hdr)
>>>>    	return cksum;
>>>>    }
>>>>
>>>> +/**
>>>> + * @internal Calculate the non-complemented IPv6 L4 checksum of a
>>>> +packet  */ static inline uint16_t
>>>> +__rte_ipv6_udptcp_cksum_mbuf(const
>>>> +struct rte_mbuf *m,
>>>> +			     const struct rte_ipv6_hdr *ipv6_hdr,
>>>> +			     uint16_t l4_off)
>>>> +{
>>>> +	uint16_t raw_cksum;
>>>> +	uint32_t cksum;
>>>> +
>>>> +	if (l4_off > m->pkt_len)
>>>> +		return 0;
>>>> +
>>>> +	if (rte_raw_cksum_mbuf(m, l4_off, m->pkt_len - l4_off,
>>> &raw_cksum))
>>>> +		return 0;
>>>> +
>>>> +	cksum = raw_cksum + rte_ipv6_phdr_cksum(ipv6_hdr, 0);
>>>> +
>>>> +	cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff);
>>> Same, please check if we can opt for __rte_raw_cksum_reduce(cksum)
>>>> +
>>>> +	return (uint16_t)cksum;
>>>> +}
>>>> +
>>>> +/**
>>>> + * @warning
>>>> + * @b EXPERIMENTAL: this API may change without prior notice.
>>>> + *
>>>> + * Process the IPv6 UDP or TCP checksum of a packet.
>>>> + *
>>>> + * The IPv6 header must not be followed by extension headers. The
>>>> +layer 4
>>>> + * checksum must be set to 0 in the L4 header by the caller.
>>>> + *
>>>> + * @param m
>>>> + *   The pointer to the mbuf.
>>>> + * @param ipv6_hdr
>>>> + *   The pointer to the contiguous IPv6 header.
>>>> + * @param l4_off
>>>> + *   The offset in bytes to start L4 checksum.
>>>> + * @return
>>>> + *   The complemented checksum to set in the L4 header.
>>>> + */
>>>> +__rte_experimental
>>>> +static inline uint16_t
>>>> +rte_ipv6_udptcp_cksum_mbuf(const struct rte_mbuf *m,
>>>> +			   const struct rte_ipv6_hdr *ipv6_hdr, uint16_t l4_off)
>>> {
>>>> +	uint16_t cksum = __rte_ipv6_udptcp_cksum_mbuf(m, ipv6_hdr,
>>> l4_off);
>>>> +
>>>> +	cksum = ~cksum;
>>>> +
>>>> +	/*
>>>> +	 * Per RFC 768: If the computed checksum is zero for UDP,
>>>> +	 * it is transmitted as all ones
>>>> +	 * (the equivalent in one's complement arithmetic).
>>>> +	 */
>>>> +	if (cksum == 0 && ipv6_hdr->proto == IPPROTO_UDP)
>>>> +		cksum = 0xffff;
>>>> +
>>>> +	return cksum;
>>>> +}
>>>> +
>>>>    /**
>>>>     * Validate the IPv6 UDP or TCP checksum.
>>>>     *
>>>> @@ -565,6 +718,39 @@ rte_ipv6_udptcp_cksum_verify(const struct
>>> rte_ipv6_hdr *ipv6_hdr,
>>>>    	return 0;
>>>>    }
>>>>
>>>> +/**
>>>> + * @warning
>>>> + * @b EXPERIMENTAL: this API may change without prior notice.
>>>> + *
>>>> + * Validate the IPv6 UDP or TCP checksum of a packet.
>>>> + *
>>>> + * In case of UDP, the caller must first check if udp_hdr->dgram_cksum is
>> 0:
>>>> + * this is either invalid or means no checksum in some situations.
>>>> +See 8.1
>>>> + * (Upper-Layer Checksums) in RFC 8200.
>>>> + *
>>>> + * @param m
>>>> + *   The pointer to the mbuf.
>>>> + * @param ipv6_hdr
>>>> + *   The pointer to the contiguous IPv6 header.
>>>> + * @param l4_off
>>>> + *   The offset in bytes to start L4 checksum.
>>>> + * @return
>>>> + *   Return 0 if the checksum is correct, else -1.
>>>> + */
>>>> +__rte_experimental
>>>> +static inline int
>>>> +rte_ipv6_udptcp_cksum_mbuf_verify(const struct rte_mbuf *m,
>>>> +				  const struct rte_ipv6_hdr *ipv6_hdr,
>>>> +				  uint16_t l4_off)
>>>> +{
>>>> +	uint16_t cksum = __rte_ipv6_udptcp_cksum_mbuf(m, ipv6_hdr,
>>> l4_off);
>>>> +
>>>> +	if (cksum != 0xffff)
>>>> +		return -1;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>>    /** IPv6 fragment extension header. */
>>>>    #define	RTE_IPV6_EHDR_MF_SHIFT	0
>>>>    #define	RTE_IPV6_EHDR_MF_MASK	1
>>>> diff --git a/lib/net/version.map b/lib/net/version.map index
>>>> 4f4330d1c4..0f2aacdef8 100644
>>>> --- a/lib/net/version.map
>>>> +++ b/lib/net/version.map
>>>> @@ -12,3 +12,13 @@ DPDK_22 {
>>>>
>>>>    	local: *;
>>>>    };
>>>> +
>>>> +EXPERIMENTAL {
>>>> +	global:
>>>> +
>>>> +	# added in 22.03
>>>> +	rte_ipv4_udptcp_cksum_mbuf;
>>>> +	rte_ipv4_udptcp_cksum_mbuf_verify;
>>>> +	rte_ipv6_udptcp_cksum_mbuf;
>>>> +	rte_ipv6_udptcp_cksum_mbuf_verify;
>>>> +};

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