[v4] net/cksum: compute raw cksum for several segments

[su sai]

Appreciate your review. I've resent the updated patch with your Acked-by
tag included.

On Thu, Jun 18, 2026 at 4:02 AM Marat Khalili <marat.khalili at huawei.com>
wrote:

> > -----Original Message-----
> > From: Su Sai <spiderdetective.ss at gmail.com>
> > Sent: Tuesday 16 June 2026 13:38
> > To: stephen at networkplumber.org
> > Cc: dev at dpdk.org; spiderdetective.ss at gmail.com
> > Subject: [v4] net/cksum: compute raw cksum for several segments
> >
> > The rte_raw_cksum_mbuf function is used to compute
> > the raw checksum of a packet.
> > If the packet payload stored in multi mbuf, the function
> > will goto the hard case. In hard case,
> > the variable 'tmp' is a type of uint32_t,
> > so rte_bswap16 will drop high 16 bit.
> > Meanwhile, the variable 'sum' is a type of uint32_t,
> > so 'sum += tmp' will drop the carry when overflow.
> > Both drop will make cksum incorrect.
> > This commit fixes the above bug.
> >
> > Signed-off-by: Su Sai <spiderdetective.ss at gmail.com>
>
> You can add:
>
> Acked-by: Marat Khalili <marat.khalili at huawei.com>
>
> > ---
> >  .mailmap              |   1 +
> >  app/test/test_cksum.c | 102 ++++++++++++++++++++++++++++++++++++++++++
> >  lib/net/rte_cksum.h   |  27 +++++++++--
> >  3 files changed, 126 insertions(+), 4 deletions(-)
> >
> > diff --git a/.mailmap b/.mailmap
> > index 4001e5fb0e..bcf73cb902 100644
> > --- a/.mailmap
> > +++ b/.mailmap
> > @@ -1630,6 +1630,7 @@ Sylvia Grundw眉rmer <sylvia.grundwuermer at b-plus.com
> >
> >  Sylwester Dziedziuch <sylwesterx.dziedziuch at intel.com>
> >  Sylwia Wnuczko <sylwia.wnuczko at intel.com>
> >  Szymon Sliwa <szs at semihalf.com>
> > +Su Sai <spiderdetective.ss at gmail.com> <susai.ss at bytedance.com>
> >  Szymon T Cudzilo <szymon.t.cudzilo at intel.com>
> >  Tadhg Kearney <tadhg.kearney at intel.com>
> >  Taekyung Kim <kim.tae.kyung at navercorp.com>
> > diff --git a/app/test/test_cksum.c b/app/test/test_cksum.c
> > index ea443382a1..5bd9723fbd 100644
> > --- a/app/test/test_cksum.c
> > +++ b/app/test/test_cksum.c
> > @@ -85,6 +85,42 @@ static const char test_cksum_ipv4_opts_udp[] = {
> >       0x00, 0x35, 0x00, 0x09, 0x89, 0x6f, 0x78,
> >  };
> >
> > +/*
> > + * generated in scapy with
> > + * Ether()/IP()/TCP(options=[NOP,NOP,Timestamps])/os.urandom(113))
> > + */
> > +static const char test_cksum_ipv4_tcp_multi_segs[] = {
> > +     0x00, 0x16, 0x3e, 0x0b, 0x6b, 0xd2, 0xee, 0xff,
> > +     0xff, 0xff, 0xff, 0xff, 0x08, 0x00, 0x45, 0x00,
> > +     0x00, 0xa5, 0x46, 0x10, 0x40, 0x00, 0x40, 0x06,
> > +     0x80, 0xb5, 0xc0, 0xa8, 0xf9, 0x1d, 0xc0, 0xa8,
> > +     0xf9, 0x1e, 0xdc, 0xa2, 0x14, 0x51, 0xbb, 0x8f,
> > +     0xa0, 0x00, 0xe4, 0x7c, 0xe4, 0xb8, 0x80, 0x10,
> > +     0x02, 0x00, 0x4b, 0xc1, 0x00, 0x00, 0x01, 0x01,
> > +     0x08, 0x0a, 0x90, 0x60, 0xf4, 0xff, 0x03, 0xc5,
> > +     0xb4, 0x19, 0x77, 0x34, 0xd4, 0xdc, 0x84, 0x86,
> > +     0xff, 0x44, 0x09, 0x63, 0x36, 0x2e, 0x26, 0x9b,
> > +     0x90, 0x70, 0xf2, 0xed, 0xc8, 0x5b, 0x87, 0xaa,
> > +     0xb4, 0x67, 0x6b, 0x32, 0x3d, 0xc4, 0xbf, 0x15,
> > +     0xa9, 0x16, 0x6c, 0x2a, 0x9d, 0xb2, 0xb7, 0x6b,
> > +     0x58, 0x44, 0x58, 0x12, 0x4b, 0x8f, 0xe5, 0x12,
> > +     0x11, 0x90, 0x94, 0x68, 0x37, 0xad, 0x0a, 0x9b,
> > +     0xd6, 0x79, 0xf2, 0xb7, 0x31, 0xcf, 0x44, 0x22,
> > +     0xc8, 0x99, 0x3f, 0xe5, 0xe7, 0xac, 0xc7, 0x0b,
> > +     0x86, 0xdf, 0xda, 0xed, 0x0a, 0x0f, 0x86, 0xd7,
> > +     0x48, 0xe2, 0xf1, 0xc2, 0x43, 0xed, 0x47, 0x3a,
> > +     0xea, 0x25, 0x2d, 0xd6, 0x60, 0x38, 0x30, 0x07,
> > +     0x28, 0xdd, 0x1f, 0x0c, 0xdd, 0x7b, 0x7c, 0xd9,
> > +     0x35, 0x9d, 0x14, 0xaa, 0xc6, 0x35, 0xd1, 0x03,
> > +     0x38, 0xb1, 0xf5,
> > +};
> > +
> > +static const uint8_t test_cksum_ipv4_tcp_multi_segs_len[] = {
> > +     66,  /* the first seg contains all headers, including L2 to L4 */
> > +     61,  /* the second seg length is odd, test byte order independent
> */
> > +     52,  /* three segs are sufficient to test the most complex
> scenarios */
> > +};
> > +
> >  /* test l3/l4 checksum api */
> >  static int
> >  test_l4_cksum(struct rte_mempool *pktmbuf_pool, const char *pktdata,
> size_t len)
> > @@ -223,6 +259,66 @@ test_l4_cksum(struct rte_mempool *pktmbuf_pool,
> const char *pktdata, size_t len)
> >       return -1;
> >  }
> >
> > +/* test l4 checksum api for a packet with multiple mbufs */
> > +static int
> > +test_l4_cksum_multi_mbufs(struct rte_mempool *pktmbuf_pool, const char
> *pktdata, size_t len,
> > +                          const uint8_t *segs, size_t segs_len)
> > +{
> > +     struct rte_mbuf *m[NB_MBUF] = {0};
> > +     struct rte_mbuf *m_hdr = NULL;
> > +     struct rte_net_hdr_lens hdr_lens;
> > +     size_t i, off = 0;
> > +     uint32_t packet_type, l3;
> > +     void *l3_hdr;
> > +     char *data;
> > +
> > +     for (i = 0; i < segs_len; i++) {
> > +             m[i] = rte_pktmbuf_alloc(pktmbuf_pool);
> > +             if (m[i] == NULL)
> > +                     GOTO_FAIL("Cannot allocate mbuf");
> > +
> > +             data = rte_pktmbuf_append(m[i], segs[i]);
> > +             if (data == NULL)
> > +                     GOTO_FAIL("Cannot append data");
> > +
> > +             memcpy(data, pktdata + off, segs[i]);
> > +             off += segs[i];
> > +
> > +             if (m_hdr) {
> > +                     if (rte_pktmbuf_chain(m_hdr, m[i]))
> > +                             GOTO_FAIL("Cannot chain mbuf");
> > +             } else {
> > +                     m_hdr = m[i];
> > +             }
> > +     }
> > +
> > +     if (off != len)
> > +             GOTO_FAIL("Invalid segs");
> > +
> > +     packet_type = rte_net_get_ptype(m_hdr, &hdr_lens,
> RTE_PTYPE_ALL_MASK);
> > +     l3 = packet_type & RTE_PTYPE_L3_MASK;
> > +
> > +     l3_hdr = rte_pktmbuf_mtod_offset(m_hdr, void *, hdr_lens.l2_len);
> > +     off = hdr_lens.l2_len + hdr_lens.l3_len;
> > +
> > +     if (l3 == RTE_PTYPE_L3_IPV4 || l3 == RTE_PTYPE_L3_IPV4_EXT) {
> > +             if (rte_ipv4_udptcp_cksum_mbuf_verify(m_hdr, l3_hdr, off)
> != 0)
> > +                     GOTO_FAIL("Invalid L4 checksum verification for
> multiple mbufs");
> > +     } else if (l3 == RTE_PTYPE_L3_IPV6 || l3 == RTE_PTYPE_L3_IPV6_EXT)
> {
> > +             if (rte_ipv6_udptcp_cksum_mbuf_verify(m_hdr, l3_hdr, off)
> != 0)
> > +                     GOTO_FAIL("Invalid L4 checksum verification for
> multiple mbufs");
> > +     }
> > +
> > +     rte_pktmbuf_free_bulk(m, segs_len);
> > +
> > +     return 0;
> > +
> > +fail:
> > +     rte_pktmbuf_free_bulk(m, segs_len);
> > +
> > +     return -1;
> > +}
> > +
> >  static int
> >  test_cksum(void)
> >  {
> > @@ -256,6 +352,12 @@ test_cksum(void)
> >                         sizeof(test_cksum_ipv4_opts_udp)) < 0)
> >               GOTO_FAIL("checksum error on ipv4_opts_udp");
> >
> > +     if (test_l4_cksum_multi_mbufs(pktmbuf_pool,
> test_cksum_ipv4_tcp_multi_segs,
> > +                       sizeof(test_cksum_ipv4_tcp_multi_segs),
> > +                       test_cksum_ipv4_tcp_multi_segs_len,
> > +                       sizeof(test_cksum_ipv4_tcp_multi_segs_len)) < 0)
> > +             GOTO_FAIL("checksum error on multi mbufs check");
> > +
> >       rte_mempool_free(pktmbuf_pool);
> >
> >       return 0;
> > diff --git a/lib/net/rte_cksum.h b/lib/net/rte_cksum.h
> > index a8e8927952..679ba82eb6 100644
> > --- a/lib/net/rte_cksum.h
> > +++ b/lib/net/rte_cksum.h
> > @@ -80,6 +80,25 @@ __rte_raw_cksum_reduce(uint32_t sum)
> >       return (uint16_t)sum;
> >  }
> >
> > +/**
> > + * @internal Reduce a sum to the non-complemented checksum.
> > + * Helper routine for the rte_raw_cksum_mbuf().
> > + *
> > + * @param sum
> > + *   Value of the sum.
> > + * @return
> > + *   The non-complemented checksum.
> > + */
> > +static inline uint16_t
> > +__rte_raw_cksum_reduce_u64(uint64_t sum)
> > +{
> > +     uint32_t tmp;
> > +
> > +     tmp = __rte_raw_cksum_reduce((uint32_t)sum);
> > +     tmp += __rte_raw_cksum_reduce((uint32_t)(sum >> 32));
> > +     return __rte_raw_cksum_reduce(tmp);
> > +}
> > +
> >  /**
> >   * Process the non-complemented checksum of a buffer.
> >   *
> > @@ -119,8 +138,8 @@ rte_raw_cksum_mbuf(const struct rte_mbuf *m,
> uint32_t off, uint32_t len,
> >  {
> >       const struct rte_mbuf *seg;
> >       const char *buf;
> > -     uint32_t sum, tmp;
> > -     uint32_t seglen, done;
> > +     uint32_t seglen, done, tmp;
> > +     uint64_t sum;
> >
> >       /* easy case: all data in the first segment */
> >       if (off + len <= rte_pktmbuf_data_len(m)) {
> > @@ -157,7 +176,7 @@ rte_raw_cksum_mbuf(const struct rte_mbuf *m,
> uint32_t off, uint32_t len,
> >       for (;;) {
> >               tmp = __rte_raw_cksum(buf, seglen, 0);
> >               if (done & 1)
> > -                     tmp = rte_bswap16((uint16_t)tmp);
> > +                     tmp = rte_bswap32(tmp);
> >               sum += tmp;
> >               done += seglen;
> >               if (done == len)
> > @@ -169,7 +188,7 @@ rte_raw_cksum_mbuf(const struct rte_mbuf *m,
> uint32_t off, uint32_t len,
> >                       seglen = len - done;
> >       }
> >
> > -     *cksum = __rte_raw_cksum_reduce(sum);
> > +     *cksum = __rte_raw_cksum_reduce_u64(sum);
> >       return 0;
> >  }
> >
> > --
> > 2.20.1
>
>
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