Re: [dpdk-dev] [PATCH] ip_frag: modify the fragment offset and mf

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> From: huichao cai <chcchc88@163.com>
> 
> According to RFC791,the fragment offset value should be
> calculated based on the long datagram,the more fragments flag
> for the last fragment carries the same value as the long datagram.

Have to admit, that commit log is really cryptic.
I couldn't figure out what it is about till I read the actual code.
As I understand what that patch does - fixes the case when we have
to fragment already fragmented ip datagram, correct?
The code changes itself look ok to me.
Can I ask you to do few things:
1. Reword commit message, it is really misleading right now.
    Also if is a fix, then you need to follow:
    https://doc.dpdk.org/guides/contributing/patches.html#patch-fix-related-issues
2. Add new test-case for it into  app/test/test_ipfrag.c

Thanks

> 
> Signed-off-by: huichao cai <chcchc88@163.com>
> ---
>  lib/ip_frag/rte_ipv4_fragmentation.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/ip_frag/rte_ipv4_fragmentation.c b/lib/ip_frag/rte_ipv4_fragmentation.c
> index 2e7739d..fead5a9 100644
> --- a/lib/ip_frag/rte_ipv4_fragmentation.c
> +++ b/lib/ip_frag/rte_ipv4_fragmentation.c
> @@ -75,7 +75,7 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
>  	uint32_t out_pkt_pos, in_seg_data_pos;
>  	uint32_t more_in_segs;
>  	uint16_t fragment_offset, flag_offset, frag_size, header_len;
> -	uint16_t frag_bytes_remaining;
> +	uint16_t frag_bytes_remaining, not_last_frag;
> 
>  	/*
>  	 * Formal parameter checking.
> @@ -116,7 +116,9 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
>  	in_seg = pkt_in;
>  	in_seg_data_pos = header_len;
>  	out_pkt_pos = 0;
> -	fragment_offset = 0;
> +	fragment_offset = (uint16_t)((flag_offset &
> +	    RTE_IPV4_HDR_OFFSET_MASK) << RTE_IPV4_HDR_FO_SHIFT);
> +	not_last_frag = (uint16_t)(flag_offset & IPV4_HDR_MF_MASK);
> 
>  	more_in_segs = 1;
>  	while (likely(more_in_segs)) {
> @@ -186,7 +188,8 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
> 
>  		__fill_ipv4hdr_frag(out_hdr, in_hdr, header_len,
>  		    (uint16_t)out_pkt->pkt_len,
> -		    flag_offset, fragment_offset, more_in_segs);
> +		    flag_offset, fragment_offset,
> +		    not_last_frag || more_in_segs);
> 
>  		fragment_offset = (uint16_t)(fragment_offset +
>  		    out_pkt->pkt_len - header_len);
> --
> 1.8.3.1