Re: [Qemu-devel] [PATCHv7 7/9] slirp: Handle IPv6 in TCP functions

[Thomas Huth]

On 08.02.2016 11:28, Samuel Thibault wrote:
> From: Guillaume Subiron <address@hidden>
> 
> This patch adds IPv6 case in TCP functions refactored by the last
> patches.
> This also adds IPv6 pseudo-header in tcpiphdr structure.
> Finally, tcp_input() is called by ip6_input().
> 
> Signed-off-by: Guillaume Subiron <address@hidden>
> Signed-off-by: Samuel Thibault <address@hidden>
> ---
...
> diff --git a/slirp/tcp_input.c b/slirp/tcp_input.c
> index eb0df81..5840471 100644
> --- a/slirp/tcp_input.c
> +++ b/slirp/tcp_input.c
> @@ -216,7 +216,8 @@ present:
>  void
>  tcp_input(struct mbuf *m, int iphlen, struct socket *inso, unsigned short af)
>  {
> -     struct ip save_ip, *ip;
> +     struct ip save_ip, *ip;
> +     struct ip6 save_ip6, *ip6;
>       register struct tcpiphdr *ti;
>       caddr_t optp = NULL;
>       int optlen = 0;
> @@ -230,6 +231,7 @@ tcp_input(struct mbuf *m, int iphlen, struct socket 
> *inso, unsigned short af)
>       int ret;
>       struct sockaddr_storage lhost, fhost;
>       struct sockaddr_in *lhost4, *fhost4;
> +     struct sockaddr_in6 *lhost6, *fhost6;
>      struct ex_list *ex_ptr;
>      Slirp *slirp;
>  
> @@ -256,6 +258,11 @@ tcp_input(struct mbuf *m, int iphlen, struct socket 
> *inso, unsigned short af)
>       }
>       slirp = m->slirp;
>  
> +     ip = mtod(m, struct ip *);
> +     ip6 = mtod(m, struct ip6 *);
> +     save_ip = *ip;
> +     save_ip6 = *ip6;

Could you do the "save_ip = *ip" within the "case AF_INET" below, and
the "save_ip6 = *ip6" within the case AF_INET6 ? That would avoid to
copy bytes that are not required.

>       switch (af) {
>       case AF_INET:
>           if (iphlen > sizeof(struct ip)) {
> @@ -264,13 +271,6 @@ tcp_input(struct mbuf *m, int iphlen, struct socket 
> *inso, unsigned short af)
>           }
>           /* XXX Check if too short */
>  
> -
> -         /*
> -          * Save a copy of the IP header in case we want restore it
> -          * for sending an ICMP error message in response.
> -          */
> -         ip = mtod(m, struct ip *);
> -         save_ip = *ip;
>           save_ip.ip_len += iphlen;
>  
>           /*
> @@ -295,16 +295,35 @@ tcp_input(struct mbuf *m, int iphlen, struct socket 
> *inso, unsigned short af)
>           ti->ti_dst = save_ip.ip_dst;
>           ti->ti_pr = save_ip.ip_p;
>           ti->ti_len = htons((uint16_t)tlen);
> -         len = ((sizeof(struct tcpiphdr) - sizeof(struct tcphdr)) + tlen);
> -         if (cksum(m, len)) {
> -             goto drop;
> -         }
> +         break;
> +
> +     case AF_INET6:
> +         m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip6)
> +                                              + sizeof(struct tcphdr));
> +         m->m_len  += sizeof(struct tcpiphdr) - (sizeof(struct ip6)
> +                                              + sizeof(struct tcphdr));
> +         ti = mtod(m, struct tcpiphdr *);
> +
> +         tlen = ip6->ip_pl;
> +         tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
> +         memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
> +         memset(&ti->ti, 0, sizeof(ti->ti));
> +         ti->ti_x0 = 0;
> +         ti->ti_src6 = save_ip6.ip_src;
> +         ti->ti_dst6 = save_ip6.ip_dst;
> +         ti->ti_nh6 = save_ip6.ip_nh;
> +         ti->ti_len = htons((uint16_t)tlen);
>           break;
>  
>       default:
>           goto drop;
>       }
>  
> +     len = ((sizeof(struct tcpiphdr) - sizeof(struct tcphdr)) + tlen);
> +     if (cksum(m, len)) {
> +         goto drop;
> +     }
> +
>       /*
>        * Check that TCP offset makes sense,
>        * pull out TCP options and adjust length.              XXX
> @@ -350,6 +369,14 @@ findso:
>           fhost4->sin_addr = ti->ti_dst;
>           fhost4->sin_port = ti->ti_dport;
>           break;
> +     case AF_INET6:
> +         lhost6 = (struct sockaddr_in6 *) &lhost;
> +         lhost6->sin6_addr = ti->ti_src6;
> +         lhost6->sin6_port = ti->ti_sport;
> +         fhost6 = (struct sockaddr_in6 *) &fhost;
> +         fhost6->sin6_addr = ti->ti_dst6;
> +         fhost6->sin6_port = ti->ti_dport;
> +         break;
>       default:
>           goto drop;
>       }
> @@ -409,7 +436,6 @@ findso:
>                 so->so_iptos = ((struct ip *)ti)->ip_tos;
>                 break;
>             default:
> -               goto drop;
>                 break;
>             }
>         }
> @@ -643,6 +669,9 @@ findso:
>             case AF_INET:
>                 *ip = save_ip;
>                 break;
> +           case AF_INET6:
> +               *ip6 = save_ip6;
> +               break;
>             default:
>                 goto drop;
>             }
> @@ -1518,7 +1547,12 @@ tcp_mss(struct tcpcb *tp, u_int offer)
>           mss = min(IF_MTU, IF_MRU) - sizeof(struct tcphdr)
>                                     + sizeof(struct ip);
>           break;
> +     case AF_INET6:
> +         mss = min(IF_MTU, IF_MRU) - sizeof(struct tcphdr)
> +                                   + sizeof(struct ip6);
> +         break;
>       default:
> +         g_assert_not_reached();
>           break;
>       }
...

 Thomas