diff options
| -rw-r--r-- | drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c | 115 | ||||
| -rw-r--r-- | include/linux/if_rmnet.h | 2 |
2 files changed, 41 insertions, 76 deletions
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c index d4d23ab446ef..a6ce22f60a00 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c @@ -35,10 +35,8 @@ rmnet_map_ipv4_dl_csum_trailer(struct sk_buff *skb, { struct iphdr *ip4h = (struct iphdr *)skb->data; void *txporthdr = skb->data + ip4h->ihl * 4; - __sum16 *csum_field, csum_temp, pseudo_csum; + __sum16 *csum_field, pseudo_csum; __sum16 ip_payload_csum; - u16 csum_value_final; - __be16 addend; /* Computing the checksum over just the IPv4 header--including its * checksum field--should yield 0. If it doesn't, the IP header @@ -77,41 +75,32 @@ rmnet_map_ipv4_dl_csum_trailer(struct sk_buff *skb, * We verified above that the IP header contributes zero to the * trailer checksum. Therefore the checksum in the trailer is * just the checksum computed over the IP payload. + + * If the IP payload arrives intact, adding the pseudo header + * checksum to the IP payload checksum will yield 0xffff (negative + * zero). This means the trailer checksum and the pseudo checksum + * are additive inverses of each other. Put another way, the + * message passes the checksum test if the trailer checksum value + * is the negated pseudo header checksum. + * + * Knowing this, we don't even need to examine the transport + * header checksum value; it is already accounted for in the + * checksum value found in the trailer. */ - ip_payload_csum = (__force __sum16)~csum_trailer->csum_value; - - pseudo_csum = ~csum_tcpudp_magic(ip4h->saddr, ip4h->daddr, - ntohs(ip4h->tot_len) - ip4h->ihl * 4, - ip4h->protocol, 0); - addend = (__force __be16)pseudo_csum; - pseudo_csum = csum16_add(ip_payload_csum, addend); - - addend = (__force __be16)*csum_field; - csum_temp = ~csum16_sub(pseudo_csum, addend); - csum_value_final = (__force u16)csum_temp; - - if (unlikely(csum_value_final == 0)) { - switch (ip4h->protocol) { - case IPPROTO_UDP: - /* RFC 768 - DL4 1's complement rule for UDP csum 0 */ - csum_value_final = ~csum_value_final; - break; - - case IPPROTO_TCP: - /* DL4 Non-RFC compliant TCP checksum found */ - if (*csum_field == (__force __sum16)0xFFFF) - csum_value_final = ~csum_value_final; - break; - } - } + ip_payload_csum = csum_trailer->csum_value; - if (csum_value_final == (__force u16)*csum_field) { - priv->stats.csum_ok++; - return 0; - } else { + pseudo_csum = csum_tcpudp_magic(ip4h->saddr, ip4h->daddr, + ntohs(ip4h->tot_len) - ip4h->ihl * 4, + ip4h->protocol, 0); + + /* The cast is required to ensure only the low 16 bits are examined */ + if (ip_payload_csum != (__sum16)~pseudo_csum) { priv->stats.csum_validation_failed++; return -EINVAL; } + + priv->stats.csum_ok++; + return 0; } #if IS_ENABLED(CONFIG_IPV6) @@ -122,13 +111,9 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb, { struct ipv6hdr *ip6h = (struct ipv6hdr *)skb->data; void *txporthdr = skb->data + sizeof(*ip6h); - __sum16 *csum_field, pseudo_csum, csum_temp; - __be16 ip6_hdr_csum, addend; + __sum16 *csum_field, pseudo_csum; __sum16 ip6_payload_csum; __be16 ip_header_csum; - u16 csum_value_final; - __be16 csum_value; - u32 length; /* Checksum offload is only supported for UDP and TCP protocols; * the packet cannot include any IPv6 extension headers @@ -145,48 +130,28 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb, * of the IP header from the trailer checksum. We then add the * checksum computed over the pseudo header. */ - csum_value = ~csum_trailer->csum_value; ip_header_csum = (__force __be16)ip_fast_csum(ip6h, sizeof(*ip6h) / 4); - ip6_hdr_csum = (__force __be16)~ip_header_csum; - ip6_payload_csum = csum16_sub((__force __sum16)csum_value, - ip6_hdr_csum); - - length = (ip6h->nexthdr == IPPROTO_UDP) ? - ntohs(((struct udphdr *)txporthdr)->len) : - ntohs(ip6h->payload_len); - pseudo_csum = ~csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr, - length, ip6h->nexthdr, 0); - addend = (__force __be16)pseudo_csum; - pseudo_csum = csum16_add(ip6_payload_csum, addend); - - addend = (__force __be16)*csum_field; - csum_temp = ~csum16_sub(pseudo_csum, addend); - csum_value_final = (__force u16)csum_temp; - - if (unlikely(csum_value_final == 0)) { - switch (ip6h->nexthdr) { - case IPPROTO_UDP: - /* RFC 2460 section 8.1 - * DL6 One's complement rule for UDP checksum 0 - */ - csum_value_final = ~csum_value_final; - break; - - case IPPROTO_TCP: - /* DL6 Non-RFC compliant TCP checksum found */ - if (*csum_field == (__force __sum16)0xFFFF) - csum_value_final = ~csum_value_final; - break; - } - } + ip6_payload_csum = csum16_sub(csum_trailer->csum_value, ip_header_csum); - if (csum_value_final == (__force u16)*csum_field) { - priv->stats.csum_ok++; - return 0; - } else { + pseudo_csum = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr, + ntohs(ip6h->payload_len), + ip6h->nexthdr, 0); + + /* It's sufficient to compare the IP payload checksum with the + * negated pseudo checksum to determine whether the packet + * checksum was good. (See further explanation in comments + * in rmnet_map_ipv4_dl_csum_trailer()). + * + * The cast is required to ensure only the low 16 bits are + * examined. + */ + if (ip6_payload_csum != (__sum16)~pseudo_csum) { priv->stats.csum_validation_failed++; return -EINVAL; } + + priv->stats.csum_ok++; + return 0; } #endif diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h index be17610a981e..10e7521ecb6c 100644 --- a/include/linux/if_rmnet.h +++ b/include/linux/if_rmnet.h @@ -25,7 +25,7 @@ struct rmnet_map_dl_csum_trailer { u8 flags; /* MAP_CSUM_DL_VALID_FLAG */ __be16 csum_start_offset; __be16 csum_length; - __be16 csum_value; + __sum16 csum_value; } __aligned(1); /* rmnet_map_dl_csum_trailer flags field: |