Re: [Qemu-devel] [RFC PATCH V3 4/4] colo-compare: add TCP, UDP, ICMP packet comparison

[Jason Wang <jasowang@redhat.com>]

On 04/18/2016 07:11 PM, Zhang Chen wrote:
> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> ---
>  net/colo-compare.c | 158 +++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 154 insertions(+), 4 deletions(-)

I'm not a tcp expert, this patch may need some guys who are good at TCP
to review.

> diff --git a/net/colo-compare.c b/net/colo-compare.c
> index 4b5a2d4..3dad461 100644
> --- a/net/colo-compare.c
> +++ b/net/colo-compare.c
> @@ -385,9 +385,148 @@ static int colo_packet_compare(Packet *ppkt, Packet *spkt)
>      }
>  }
>  
> -static int colo_packet_compare_all(Packet *spkt, Packet *ppkt)
> +/*
> + * called from the compare thread on the primary
> + * for compare tcp packet
> + * compare_tcp copied from Dr. David Alan Gilbert's branch
> + */
> +static int colo_packet_compare_tcp(Packet *spkt, Packet *ppkt)
> +{
> +    struct tcphdr *ptcp, *stcp;
> +    int res;
> +    char *sdebug, *ddebug;
> +    ptrdiff_t offset;
> +
> +    trace_colo_compare_main("compare tcp");
> +    ptcp = (struct tcphdr *)ppkt->transport_layer;
> +    stcp = (struct tcphdr *)spkt->transport_layer;
> +
> +    /* Initial is compare the whole packet */
> +    offset = 12; /* Hack! Skip virtio header */

So this won't work for e1000 I believe?

> +
> +    if (ptcp->th_flags == stcp->th_flags &&
> +        ((ptcp->th_flags & (TH_ACK | TH_SYN)) == (TH_ACK | TH_SYN))) {
> +        /* This is the syn/ack response from the guest to an incoming
> +         * connection; the secondary won't have matched the sequence number
> +         * Note: We should probably compare the IP level?
> +         * Note hack: This already has the virtio offset
> +         */
> +        offset = sizeof(ptcp->th_ack) + (void *)&ptcp->th_ack - ppkt->data;
> +    }
> +    /* Note - we want to compare everything as long as it's not the syn/ack? */
> +    assert(offset > 0);
> +    assert(spkt->size > offset);
> +
> +    /* The 'identification' field in the IP header is *very* random
> +     * it almost never matches.  Fudge this by ignoring differences in
> +     * unfragmented packets; they'll normally sort themselves out if different
> +     * anyway, and it should recover at the TCP level.
> +     * An alternative would be to get both the primary and secondary to rewrite
> +     * somehow; but that would need some sync traffic to sync the state

This is very tricky I believe, I wonder this will work. Would it be
easier if we reassembly the packet?

And I believe we should check for the length before all the other
examinations?

> +     */
> +    if (ntohs(ppkt->ip->ip_off) & IP_DF) {
> +        spkt->ip->ip_id = ppkt->ip->ip_id;
> +        /* and the sum will be different if the IDs were different */
> +        spkt->ip->ip_sum = ppkt->ip->ip_sum;
> +    }
> +
> +    res = memcmp(ppkt->data + offset, spkt->data + offset,
> +                 (spkt->size - offset));
> +
> +    if (res && DEBUG_TCP_COMPARE) {
> +        sdebug = strdup(inet_ntoa(ppkt->ip->ip_src));
> +        ddebug = strdup(inet_ntoa(ppkt->ip->ip_dst));
> +        fprintf(stderr, "%s: src/dst: %s/%s offset=%zd p: seq/ack=%u/%u"
> +        " s: seq/ack=%u/%u res=%d flags=%x/%x\n", __func__,
> +                   sdebug, ddebug, offset,
> +                   ntohl(ptcp->th_seq), ntohl(ptcp->th_ack),
> +                   ntohl(stcp->th_seq), ntohl(stcp->th_ack),
> +                   res, ptcp->th_flags, stcp->th_flags);
> +        if (res && (ptcp->th_seq == stcp->th_seq)) {
> +            trace_colo_compare_with_int("Primary len", ppkt->size);
> +            colo_dump_packet(ppkt);
> +            trace_colo_compare_with_int("Secondary len", spkt->size);
> +            colo_dump_packet(spkt);
> +        }
> +        g_free(sdebug);
> +        g_free(ddebug);
> +    }
> +
> +    return res;
> +}
> +
> +/*
> + * called from the compare thread on the primary
> + * for compare udp packet
> + */
> +static int colo_packet_compare_udp(Packet *spkt, Packet *ppkt)
> +{
> +    int ret = 1;
> +
> +    trace_colo_compare_main("compare udp");
> +    ret = colo_packet_compare(ppkt, spkt);
> +
> +    if (ret) {
> +        trace_colo_compare_main("primary udp");
> +        colo_dump_packet(ppkt);
> +        trace_colo_compare_main("secondary udp");
> +        colo_dump_packet(spkt);
> +    }
> +
> +    return ret;
> +}
> +
> +/*
> + * called from the compare thread on the primary
> + * for compare icmp packet
> + */
> +static int colo_packet_compare_icmp(Packet *spkt, Packet *ppkt)
> +{
> +    int network_length;
> +    struct icmp *icmp_ppkt, *icmp_spkt;
> +
> +    trace_colo_compare_main("compare icmp");
> +    network_length = (ppkt->ip->ip_hl & 0x0F) * 4;
> +    icmp_ppkt = (struct icmp *)(ppkt->data + network_length + ETH_HLEN);
> +    icmp_spkt = (struct icmp *)(spkt->data + network_length + ETH_HLEN);
> +
> +    if ((icmp_ppkt->icmp_type == icmp_spkt->icmp_type) &&
> +        (icmp_ppkt->icmp_code == icmp_spkt->icmp_code)) {
> +        if (icmp_ppkt->icmp_type == ICMP_REDIRECT) {
> +            if (icmp_ppkt->icmp_gwaddr.s_addr !=
> +                icmp_spkt->icmp_gwaddr.s_addr) {
> +                trace_colo_compare_main("icmp_gwaddr.s_addr not same");
> +                trace_colo_compare_with_char("ppkt s_addr",
> +                        inet_ntoa(icmp_ppkt->icmp_gwaddr));
> +                trace_colo_compare_with_char("spkt s_addr",
> +                        inet_ntoa(icmp_spkt->icmp_gwaddr));
> +                return -1;
> +            }
> +        } else if ((icmp_ppkt->icmp_type == ICMP_UNREACH) &&
> +                   (icmp_ppkt->icmp_type == ICMP_UNREACH_NEEDFRAG)) {
> +            if (icmp_ppkt->icmp_nextmtu != icmp_spkt->icmp_nextmtu) {
> +                trace_colo_compare_main("icmp_nextmtu not same");
> +                trace_colo_compare_with_int("ppkt s_addr",
> +                                             icmp_ppkt->icmp_nextmtu);
> +                trace_colo_compare_with_int("spkt s_addr",
> +                                             icmp_spkt->icmp_nextmtu);
> +                return -1;
> +            }
> +        }
> +    } else {
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +/*
> + * called from the compare thread on the primary
> + * for compare other packet
> + */
> +static int colo_packet_compare_other(Packet *spkt, Packet *ppkt)
>  {
> -    trace_colo_compare_main("compare all");
> +    trace_colo_compare_main("compare other");
>      return colo_packet_compare(ppkt, spkt);
>  }
>  
> @@ -406,8 +545,19 @@ static void colo_compare_connection(void *opaque, void *user_data)
>      while (!g_queue_is_empty(&conn->primary_list) &&
>             !g_queue_is_empty(&conn->secondary_list)) {
>          pkt = g_queue_pop_head(&conn->primary_list);
> -        result = g_queue_find_custom(&conn->secondary_list,
> -                              pkt, (GCompareFunc)colo_packet_compare_all);
> +        if (conn->ip_proto == IPPROTO_TCP) {
> +            result = g_queue_find_custom(&conn->secondary_list,
> +                        pkt, (GCompareFunc)colo_packet_compare_tcp);
> +        } else if (conn->ip_proto == IPPROTO_UDP) {
> +            result = g_queue_find_custom(&conn->secondary_list,
> +                        pkt, (GCompareFunc)colo_packet_compare_udp);
> +        } else if (conn->ip_proto == IPPROTO_ICMP) {
> +            result = g_queue_find_custom(&conn->secondary_list,
> +                        pkt, (GCompareFunc)colo_packet_compare_icmp);
> +        } else {
> +            result = g_queue_find_custom(&conn->secondary_list,
> +                        pkt, (GCompareFunc)colo_packet_compare_other);
> +        }
>  

A switch...case looks better.

>          if (result) {
>              ret = compare_chr_send(pkt->s->chr_out, pkt->data, pkt->size);