[PATCH 3/6] ip_frag: include protocol in IPv4 reassembly key

[Konstantin Ananyev]

> DPDK IPv4 reassembly code was not following RFC 791 section 3.2
> which says:
>     The internet identification field (ID) is used together with the
>     source and destination address, and the protocol fields, to identify
>     datagram fragments for reassembly.
> 
> Omitting the protocol means two datagrams between the
> same pair of hosts that share an IP id but carry different protocols
> (for example UDP and ICMP) are merged into a single reassembly context,
> producing a corrupted datagram.
> 
> Fold the protocol into the unused upper bits of the 32-bit id field
> of the key. The IPv4 identification is 16 bits and occupies the low
> half, so the protocol can be carried in the upper bits without changing
> the key layout, the key comparison or the hash.
> 
> Fixes: cc8f4d020c0b ("examples/ip_reassembly: initial import")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> ---
>  lib/ip_frag/rte_ipv4_reassembly.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/ip_frag/rte_ipv4_reassembly.c b/lib/ip_frag/rte_ipv4_reassembly.c
> index 3c8ae113ba..980f7a3b77 100644
> --- a/lib/ip_frag/rte_ipv4_reassembly.c
> +++ b/lib/ip_frag/rte_ipv4_reassembly.c
> @@ -111,9 +111,15 @@ rte_ipv4_frag_reassemble_packet(struct rte_ip_frag_tbl
> *tbl,
>  	ip_ofs = (uint16_t)(flag_offset & RTE_IPV4_HDR_OFFSET_MASK);
>  	ip_flag = (uint16_t)(flag_offset & RTE_IPV4_HDR_MF_FLAG);
> 
> +	/*
> +	 * RFC 791 requires using: source, destination, identifier field and
> protocol
> +	 */
> +
>  	/* use first 8 bytes only */
>  	memcpy(&key.src_dst[0], &ip_hdr->src_addr, 8);
> -	key.id = ip_hdr->packet_id;
> +
> +	/* packet_id is 16 bits and proto id is 8 bits */
> +	key.id = ((uint32_t) ip_hdr->next_proto_id << 16) | ip_hdr->packet_id;
>  	key.key_len = IPV4_KEYLEN;
> 
>  	ip_ofs *= RTE_IPV4_HDR_OFFSET_UNITS;
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev at huawei.com>

> 2.53.0