Re: [EXT] [PATCH] ipsec: fix NAT-T length calculation

[Xiao Liang <shaw.leon@gmail.com>]

Well, let me explain.

> >>> diff --git a/lib/ipsec/esp_outb.c b/lib/ipsec/esp_outb.c
> >>> index 9cbd9202f6..ec87b1dce2 100644
> >>> --- a/lib/ipsec/esp_outb.c
> >>> +++ b/lib/ipsec/esp_outb.c
> >>> @@ -198,7 +198,7 @@ outb_tun_pkt_prepare(struct rte_ipsec_sa *sa,
> >>> rte_be64_t sqc,
> >>>             struct rte_udp_hdr *udph = (struct rte_udp_hdr *)
> >>>                     (ph + sa->hdr_len - sizeof(struct rte_udp_hdr));
> >>>             udph->dgram_len = rte_cpu_to_be_16(mb->pkt_len - sqh_len -
> >>> -                           sa->hdr_l3_off - sa->hdr_len);
> >>> +                           sa->hdr_len + sizeof(struct rte_udp_hdr));
> > To be honest, it is not clear to me why we shouldn't take into account sa->hdr_l3_off
> >   any more.
> > Probably the author can explain.
> > Also would like author of  NAT-T support to chime in.
> > Radu, any comments on that patch?
> I agree, hdr_l3_off should not be ignored. Also sa->hdr_len already
> includes the size of UDP header, see line 366 in esp_outb_tun_init in
> sa.c (or the line above this change, where the udph pointer is computed
> assuming this)

A few lines above, there is:

    ph = rte_pktmbuf_prepend(mb, hlen - l2len);

The L2 header is already pulled from the packet, then the packet
length has nothing to do with hdr_l3_off from this point, so use encap
header length instead.
You are right sa->hdr_len already includes the size of UDP header, and
that's why it should be added back here.

> >>>     }
> >>>
> >>>     /* update original and new ip header fields */
> >>> diff --git a/lib/ipsec/sa.c b/lib/ipsec/sa.c
> >>> index 59a547637d..2297bd6d72 100644
> >>> --- a/lib/ipsec/sa.c
> >>> +++ b/lib/ipsec/sa.c
> >>> @@ -371,7 +371,7 @@ esp_outb_tun_init(struct rte_ipsec_sa *sa, const struct
> >>> rte_ipsec_sa_prm *prm)
> >>>
> >>>     /* update l2_len and l3_len fields for outbound mbuf */
> >>>     sa->tx_offload.val = rte_mbuf_tx_offload(sa->hdr_l3_off,
> >>> -           sa->hdr_len - sa->hdr_l3_off, 0, 0, 0, 0, 0);
> >>> +           prm->tun.hdr_len - sa->hdr_l3_off, 0, 0, 0, 0, 0);
> >>>
> >>>     esp_outb_init(sa, sa->hdr_len, prm->ipsec_xform.esn.value);
> >>>   }

Again sa->hdr_len includes UDP header, which is not part of L3, so use
the original prm->tun.hdr_len.

Thanks,
Xiao Liang