RE: [PATCH v2 4/4] net/colo: Match is-enabled probe to tracepoint

["Zhang, Chen" <chen.zhang@intel.com>]

> -----Original Message-----
> From: Roman Bolshakov <r.bolshakov@yadro.com>
> Sent: Friday, July 17, 2020 5:35 PM
> To: qemu-devel@nongnu.org
> Cc: Daniel P. Berrangé <berrange@redhat.com>; Stefan Hajnoczi
> <stefanha@redhat.com>; Cameron Esfahani <dirty@apple.com>; Roman
> Bolshakov <r.bolshakov@yadro.com>; Philippe Mathieu-Daudé
> <philmd@redhat.com>; Zhang, Chen <chen.zhang@intel.com>; Li Zhijian
> <lizhijian@cn.fujitsu.com>; Jason Wang <jasowang@redhat.com>
> Subject: [PATCH v2 4/4] net/colo: Match is-enabled probe to tracepoint
> 
> Build of QEMU with dtrace fails on macOS:
> 
>   LINK    x86_64-softmmu/qemu-system-x86_64
> error: probe colo_compare_miscompare doesn't exist
> error: Could not register probes
> ld: error creating dtrace DOF section for architecture x86_64
> 
> The reason of the error is explained by Adam Leventhal [1]:
> 
>   Note that is-enabled probes don't have the stability magic so I'm not
>   sure how things would work if only is-enabled probes were used.
> 
> net/colo code uses is-enabled probes to determine if other probes should be
> used but colo_compare_miscompare itself is not used explicitly.
> Linker doesn't include the symbol and build fails.
> 
> The issue can be resolved if is-enabled probe matches the actual trace point
> that is used inside the test. Packet dump toggle is replaced with a compile-
> time conditional definition.
> 
> 1. http://markmail.org/message/6grq2ygr5nwdwsnb
> 
> Fixes: f4b618360e ("colo-compare: add TCP, UDP, ICMP packet comparison")
> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
> Cc: Cameron Esfahani <dirty@apple.com>
> Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
> ---
>  net/colo-compare.c    | 42 ++++++++++++++++++++++--------------------
>  net/filter-rewriter.c | 10 ++++++++--
>  net/trace-events      |  2 --
>  3 files changed, 30 insertions(+), 24 deletions(-)
> 
> diff --git a/net/colo-compare.c b/net/colo-compare.c index
> 398b7546ff..e0be98e494 100644
> --- a/net/colo-compare.c
> +++ b/net/colo-compare.c
> @@ -54,6 +54,8 @@ static NotifierList colo_compare_notifiers =  #define
> REGULAR_PACKET_CHECK_MS 3000  #define DEFAULT_TIME_OUT_MS 3000
> 
> +/* #define DEBUG_COLO_PACKETS */
> +
>  static QemuMutex colo_compare_mutex;
>  static bool colo_compare_active;
>  static QemuMutex event_mtx;
> @@ -327,7 +329,7 @@ static int colo_compare_packet_payload(Packet
> *ppkt,
>                                         uint16_t len)
> 
>  {
> -    if
> (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE))
> {
> +    if (trace_event_get_state_backends(TRACE_COLO_COMPARE_IP_INFO))
> {
>          char pri_ip_src[20], pri_ip_dst[20], sec_ip_src[20], sec_ip_dst[20];
> 
>          strcpy(pri_ip_src, inet_ntoa(ppkt->ip->ip_src)); @@ -492,12 +494,12
> @@ sec:
>          g_queue_push_head(&conn->primary_list, ppkt);
>          g_queue_push_head(&conn->secondary_list, spkt);
> 
> -        if
> (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE))
> {
> -            qemu_hexdump((char *)ppkt->data, stderr,
> -                        "colo-compare ppkt", ppkt->size);
> -            qemu_hexdump((char *)spkt->data, stderr,
> -                        "colo-compare spkt", spkt->size);
> -        }
> +#ifdef DEBUG_COLO_PACKETS
> +        qemu_hexdump((char *)ppkt->data, stderr,
> +                     "colo-compare ppkt", ppkt->size);
> +        qemu_hexdump((char *)spkt->data, stderr,
> +                     "colo-compare spkt", spkt->size); #endif
> 
>          colo_compare_inconsistency_notify(s);
>      }
> @@ -533,12 +535,12 @@ static int colo_packet_compare_udp(Packet *spkt,
> Packet *ppkt)
>                                      ppkt->size - offset)) {
>          trace_colo_compare_udp_miscompare("primary pkt size", ppkt->size);
>          trace_colo_compare_udp_miscompare("Secondary pkt size", spkt-
> >size);
> -        if
> (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE))
> {
> -            qemu_hexdump((char *)ppkt->data, stderr, "colo-compare pri pkt",
> -                         ppkt->size);
> -            qemu_hexdump((char *)spkt->data, stderr, "colo-compare sec pkt",
> -                         spkt->size);
> -        }
> +#ifdef DEBUG_COLO_PACKETS
> +        qemu_hexdump((char *)ppkt->data, stderr, "colo-compare pri pkt",
> +                     ppkt->size);
> +        qemu_hexdump((char *)spkt->data, stderr, "colo-compare sec pkt",
> +                     spkt->size);
> +#endif

Hi Roman,

I think change the " trace_event_get_state_backends()" to "trace_colo_compare_main("Dump packet hex: ")" is a better choice here.
It will keep the original code logic and avoid the problem here.

Thanks
Zhang Chen

>          return -1;
>      } else {
>          return 0;
> @@ -576,12 +578,12 @@ static int colo_packet_compare_icmp(Packet *spkt,
> Packet *ppkt)
>                                             ppkt->size);
>          trace_colo_compare_icmp_miscompare("Secondary pkt size",
>                                             spkt->size);
> -        if
> (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE))
> {
> -            qemu_hexdump((char *)ppkt->data, stderr, "colo-compare pri pkt",
> -                         ppkt->size);
> -            qemu_hexdump((char *)spkt->data, stderr, "colo-compare sec pkt",
> -                         spkt->size);
> -        }
> +#ifdef DEBUG_COLO_PACKETS
> +        qemu_hexdump((char *)ppkt->data, stderr, "colo-compare pri pkt",
> +                     ppkt->size);
> +        qemu_hexdump((char *)spkt->data, stderr, "colo-compare sec pkt",
> +                     spkt->size);
> +#endif
>          return -1;
>      } else {
>          return 0;
> @@ -597,7 +599,7 @@ static int colo_packet_compare_other(Packet *spkt,
> Packet *ppkt)
>      uint16_t offset = ppkt->vnet_hdr_len;
> 
>      trace_colo_compare_main("compare other");
> -    if
> (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE))
> {
> +    if (trace_event_get_state_backends(TRACE_COLO_COMPARE_IP_INFO))
> {
>          char pri_ip_src[20], pri_ip_dst[20], sec_ip_src[20], sec_ip_dst[20];
> 
>          strcpy(pri_ip_src, inet_ntoa(ppkt->ip->ip_src)); diff --git a/net/filter-
> rewriter.c b/net/filter-rewriter.c index 1aaad101b6..576b019d09 100644
> --- a/net/filter-rewriter.c
> +++ b/net/filter-rewriter.c
> @@ -76,11 +76,14 @@ static int handle_primary_tcp_pkt(RewriterState *rf,
>      struct tcp_hdr *tcp_pkt;
> 
>      tcp_pkt = (struct tcp_hdr *)pkt->transport_header;
> -    if
> (trace_event_get_state_backends(TRACE_COLO_FILTER_REWRITER_DEBUG
> )) {
> +    if
> +
> (trace_event_get_state_backends(TRACE_COLO_FILTER_REWRITER_PKT_IN
> FO))
> + {
>          trace_colo_filter_rewriter_pkt_info(__func__,
>                      inet_ntoa(pkt->ip->ip_src), inet_ntoa(pkt->ip->ip_dst),
>                      ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),
>                      tcp_pkt->th_flags);
> +    }
> +    if (trace_event_get_state_backends(
> +          TRACE_COLO_FILTER_REWRITER_CONN_OFFSET)) {
>          trace_colo_filter_rewriter_conn_offset(conn->offset);
>      }
> 
> @@ -180,11 +183,14 @@ static int handle_secondary_tcp_pkt(RewriterState
> *rf,
> 
>      tcp_pkt = (struct tcp_hdr *)pkt->transport_header;
> 
> -    if
> (trace_event_get_state_backends(TRACE_COLO_FILTER_REWRITER_DEBUG
> )) {
> +    if
> +
> (trace_event_get_state_backends(TRACE_COLO_FILTER_REWRITER_PKT_IN
> FO))
> + {
>          trace_colo_filter_rewriter_pkt_info(__func__,
>                      inet_ntoa(pkt->ip->ip_src), inet_ntoa(pkt->ip->ip_dst),
>                      ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),
>                      tcp_pkt->th_flags);
> +    }
> +    if (trace_event_get_state_backends(
> +          TRACE_COLO_FILTER_REWRITER_CONN_OFFSET)) {
>          trace_colo_filter_rewriter_conn_offset(conn->offset);
>      }
> 
> diff --git a/net/trace-events b/net/trace-events index
> fa49c71533..bfaff7891d 100644
> --- a/net/trace-events
> +++ b/net/trace-events
> @@ -17,10 +17,8 @@ colo_compare_udp_miscompare(const char *sta, int
> size) ": %s = %d"
>  colo_compare_icmp_miscompare(const char *sta, int size) ": %s = %d"
>  colo_compare_ip_info(int psize, const char *sta, const char *stb, int ssize,
> const char *stc, const char *std) "ppkt size = %d, ip_src = %s, ip_dst = %s,
> spkt size = %d, ip_src = %s, ip_dst = %s"
>  colo_old_packet_check_found(int64_t old_time) "%" PRId64
> -colo_compare_miscompare(void) ""
>  colo_compare_tcp_info(const char *pkt, uint32_t seq, uint32_t ack, int
> hdlen, int pdlen, int offset, int flags) "%s: seq/ack= %u/%u hdlen= %d
> pdlen= %d offset= %d flags=%d"
> 
>  # filter-rewriter.c
> -colo_filter_rewriter_debug(void) ""
>  colo_filter_rewriter_pkt_info(const char *func, const char *src, const char
> *dst, uint32_t seq, uint32_t ack, uint32_t flag) "%s: src/dst: %s/%s p:
> seq/ack=%u/%u  flags=0x%x"
>  colo_filter_rewriter_conn_offset(uint32_t offset) ": offset=%u"
> --
> 2.26.1