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

[Thomas Huth <thuth@redhat.com>]

On 08.02.2016 11:28, Samuel Thibault wrote:
> From: Guillaume Subiron <maethor@subiron.org>
> 
> 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 <maethor@subiron.org>
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> ---
...
> 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