On Wed, 24 Nov 2021 16:47:06 +0800, Huichao Cai wrote:
> +/*
> + * Options "fragmenting", just fill options not
> + * allowed in fragments with NOOPs.
> + * Simple and stupid 8), but the most efficient way.
> + */
> +static inline void ip_options_fragment(struct rte_ipv4_hdr *iph)
> +{
> + unsigned char *optptr = (unsigned char *)iph +
> + sizeof(struct rte_ipv4_hdr);
> + int l = (iph->version_ihl & RTE_IPV4_HDR_IHL_MASK) *
> + RTE_IPV4_IHL_MULTIPLIER - sizeof(struct rte_ipv4_hdr);
> + int optlen;
> +
> + while (l > 0) {
> + switch (*optptr) {
> + case RTE_IPOPT_END:
> + return;
> + case RTE_IPOPT_NOOP:
> + l--;
> + optptr++;
> + continue;
> + }
> + optlen = optptr[1];
> + if (optlen < 2 || optlen > l)
> + return;
> + if (!RTE_IPOPT_COPIED(*optptr))
> + memset(optptr, RTE_IPOPT_NOOP, optlen);
> + l -= optlen;
> + optptr += optlen;
> + }
> +}
> +
I have a few concerns regarding this implementation:
- Any IPv4 option longer than 2 bytes with copied flag unset, will not be
substituted by NOOP option. In effect it will be copied to all fragments.
- Substituting options with NOOP might cause rte_ipv4_fragment_packet to
produce more fragments than necessary, since options with copied flag unset
will still occupy space in IPv4 header.
It would require some benchmarking, but maybe a better solution would be to
prepare a separate IPv4 header for fragments without unnecessary options.
