net: introduce functions to verify L4 checksums

Since commit d5df2ae0428a ("net: fix unneeded replacement of TCP
checksum 0"), the functions rte_ipv4_udptcp_cksum() and
rte_ipv6_udptcp_cksum() can return either 0x0000 or 0xffff when used to
verify a packet containing a valid checksum.

Since these functions should be used to calculate the checksum to set in
a packet, introduce 2 new helpers for checksum verification. They return
0 if the checksum is valid in the packet.

Use this new helper in net/tap driver.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 5429f61..2229eef 100644 (file)
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -369,11 +369,12 @@ tap_verify_csum(struct rte_mbuf *mbuf)
                                        return;
                                }
                        }
-                       cksum = rte_ipv4_udptcp_cksum(l3_hdr, l4_hdr);
+                       cksum_ok = !rte_ipv4_udptcp_cksum_verify(l3_hdr,
+                                                                l4_hdr);
                } else { /* l3 == RTE_PTYPE_L3_IPV6, checked above */
-                       cksum = rte_ipv6_udptcp_cksum(l3_hdr, l4_hdr);
+                       cksum_ok = !rte_ipv6_udptcp_cksum_verify(l3_hdr,
+                                                                l4_hdr);
                }
-               cksum_ok = (cksum == 0) || (cksum == 0xffff);
                mbuf->ol_flags |= cksum_ok ?
                        PKT_RX_L4_CKSUM_GOOD : PKT_RX_L4_CKSUM_BAD;
        }

diff --git a/lib/net/rte_ip.h b/lib/net/rte_ip.h
index 4b72896..05948b6 100644 (file)
--- a/lib/net/rte_ip.h
+++ b/lib/net/rte_ip.h
@@ -344,20 +344,10 @@ rte_ipv4_phdr_cksum(const struct rte_ipv4_hdr *ipv4_hdr, uint64_t ol_flags)
 }
 
 /**
- * Process the IPv4 UDP or TCP checksum.
- *
- * The IP and layer 4 checksum must be set to 0 in the packet by
- * the caller.
- *
- * @param ipv4_hdr
- *   The pointer to the contiguous IPv4 header.
- * @param l4_hdr
- *   The pointer to the beginning of the L4 header.
- * @return
- *   The complemented checksum to set in the IP packet.
+ * @internal Calculate the non-complemented IPv4 L4 checksum
  */
 static inline uint16_t
-rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, const void *l4_hdr)
+__rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, const void *l4_hdr)
 {
        uint32_t cksum;
        uint32_t l3_len, l4_len;
@@ -374,16 +364,65 @@ rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, const void *l4_hdr)
        cksum += rte_ipv4_phdr_cksum(ipv4_hdr, 0);
 
        cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff);
-       cksum = (~cksum) & 0xffff;
+
+       return (uint16_t)cksum;
+}
+
+/**
+ * Process the IPv4 UDP or TCP checksum.
+ *
+ * The IP and layer 4 checksum must be set to 0 in the packet by
+ * the caller.
+ *
+ * @param ipv4_hdr
+ *   The pointer to the contiguous IPv4 header.
+ * @param l4_hdr
+ *   The pointer to the beginning of the L4 header.
+ * @return
+ *   The complemented checksum to set in the IP packet.
+ */
+static inline uint16_t
+rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, const void *l4_hdr)
+{
+       uint16_t cksum = __rte_ipv4_udptcp_cksum(ipv4_hdr, l4_hdr);
+
+       cksum = ~cksum;
+
        /*
-        * Per RFC 768:If the computed checksum is zero for UDP,
+        * 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 (uint16_t)cksum;
+       return cksum;
+}
+
+/**
+ * Validate the IPv4 UDP or TCP checksum.
+ *
+ * In case of UDP, the caller must first check if udp_hdr->dgram_cksum is 0
+ * (i.e. no checksum).
+ *
+ * @param ipv4_hdr
+ *   The pointer to the contiguous IPv4 header.
+ * @param l4_hdr
+ *   The pointer to the beginning of the L4 header.
+ * @return
+ *   Return 0 if the checksum is correct, else -1.
+ */
+__rte_experimental
+static inline int
+rte_ipv4_udptcp_cksum_verify(const struct rte_ipv4_hdr *ipv4_hdr,
+                            const void *l4_hdr)
+{
+       uint16_t cksum = __rte_ipv4_udptcp_cksum(ipv4_hdr, l4_hdr);
+
+       if (cksum != 0xffff)
+               return -1;
+
+       return 0;
 }
 
 /**
@@ -448,6 +487,25 @@ rte_ipv6_phdr_cksum(const struct rte_ipv6_hdr *ipv6_hdr, uint64_t ol_flags)
        return __rte_raw_cksum_reduce(sum);
 }
 
+/**
+ * @internal Calculate the non-complemented IPv4 L4 checksum
+ */
+static inline uint16_t
+__rte_ipv6_udptcp_cksum(const struct rte_ipv6_hdr *ipv6_hdr, const void *l4_hdr)
+{
+       uint32_t cksum;
+       uint32_t l4_len;
+
+       l4_len = rte_be_to_cpu_16(ipv6_hdr->payload_len);
+
+       cksum = rte_raw_cksum(l4_hdr, l4_len);
+       cksum += rte_ipv6_phdr_cksum(ipv6_hdr, 0);
+
+       cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff);
+
+       return (uint16_t)cksum;
+}
+
 /**
  * Process the IPv6 UDP or TCP checksum.
  *
@@ -464,16 +522,10 @@ rte_ipv6_phdr_cksum(const struct rte_ipv6_hdr *ipv6_hdr, uint64_t ol_flags)
 static inline uint16_t
 rte_ipv6_udptcp_cksum(const struct rte_ipv6_hdr *ipv6_hdr, const void *l4_hdr)
 {
-       uint32_t cksum;
-       uint32_t l4_len;
+       uint16_t cksum = __rte_ipv6_udptcp_cksum(ipv6_hdr, l4_hdr);
 
-       l4_len = rte_be_to_cpu_16(ipv6_hdr->payload_len);
-
-       cksum = rte_raw_cksum(l4_hdr, l4_len);
-       cksum += rte_ipv6_phdr_cksum(ipv6_hdr, 0);
+       cksum = ~cksum;
 
-       cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff);
-       cksum = (~cksum) & 0xffff;
        /*
         * Per RFC 768: If the computed checksum is zero for UDP,
         * it is transmitted as all ones
@@ -482,7 +534,34 @@ rte_ipv6_udptcp_cksum(const struct rte_ipv6_hdr *ipv6_hdr, const void *l4_hdr)
        if (cksum == 0 && ipv6_hdr->proto == IPPROTO_UDP)
                cksum = 0xffff;
 
-       return (uint16_t)cksum;
+       return cksum;
+}
+
+/**
+ * Validate the IPv6 UDP or TCP checksum.
+ *
+ * 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 ipv6_hdr
+ *   The pointer to the contiguous IPv6 header.
+ * @param l4_hdr
+ *   The pointer to the beginning of the L4 header.
+ * @return
+ *   Return 0 if the checksum is correct, else -1.
+ */
+__rte_experimental
+static inline int
+rte_ipv6_udptcp_cksum_verify(const struct rte_ipv6_hdr *ipv6_hdr,
+                            const void *l4_hdr)
+{
+       uint16_t cksum = __rte_ipv6_udptcp_cksum(ipv6_hdr, l4_hdr);
+
+       if (cksum != 0xffff)
+               return -1;
+
+       return 0;
 }
 
 /** IPv6 fragment extension header. */