[bpf-next V4 PATCH 8/8] samples/bpf: xdp_monitor use err code from tracepoint xdp:xdp_devmap_xmit

[Jesper Dangaard Brouer]

Update xdp_monitor to use the recently added err code introduced
in tracepoint xdp:xdp_devmap_xmit, to show if the drop count is
caused by some driver general delivery problem.  Other kind of drops
will likely just be more normal TX space issues.
---
 samples/bpf/xdp_monitor_kern.c |   10 ++++++++++
 samples/bpf/xdp_monitor_user.c |   35 ++++++++++++++++++++++++++++++-----
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/samples/bpf/xdp_monitor_kern.c b/samples/bpf/xdp_monitor_kern.c
index 2854aa0665ea..ad10fe700d7d 100644
--- a/samples/bpf/xdp_monitor_kern.c
+++ b/samples/bpf/xdp_monitor_kern.c
@@ -125,6 +125,7 @@ struct datarec {
        u64 processed;
        u64 dropped;
        u64 info;
+       u64 err;
 };
 #define MAX_CPUS 64
 
@@ -228,6 +229,7 @@ struct devmap_xmit_ctx {
        int sent;               //      offset:24; size:4; signed:1;
        int from_ifindex;       //      offset:28; size:4; signed:1;
        int to_ifindex;         //      offset:32; size:4; signed:1;
+       int err;                //      offset:36; size:4; signed:1;
 };
 
 SEC("tracepoint/xdp/xdp_devmap_xmit")
@@ -245,5 +247,13 @@ int trace_xdp_devmap_xmit(struct devmap_xmit_ctx *ctx)
        /* Record bulk events, then userspace can calc average bulk size */
        rec->info += 1;
 
+       /* Record error cases, where no frame were sent */
+       if (ctx->err)
+               rec->err++;
+
+       /* Catch API error of drv ndo_xdp_xmit sent more than count */
+       if (ctx->drops < 0)
+               rec->err++;
+
        return 1;
 }
diff --git a/samples/bpf/xdp_monitor_user.c b/samples/bpf/xdp_monitor_user.c
index 7e18a454924c..dd558cbb2309 100644
--- a/samples/bpf/xdp_monitor_user.c
+++ b/samples/bpf/xdp_monitor_user.c
@@ -117,6 +117,7 @@ struct datarec {
        __u64 processed;
        __u64 dropped;
        __u64 info;
+       __u64 err;
 };
 #define MAX_CPUS 64
 
@@ -152,6 +153,7 @@ static bool map_collect_record(int fd, __u32 key, struct 
record *rec)
        __u64 sum_processed = 0;
        __u64 sum_dropped = 0;
        __u64 sum_info = 0;
+       __u64 sum_err = 0;
        int i;
 
        if ((bpf_map_lookup_elem(fd, &key, values)) != 0) {
@@ -170,10 +172,13 @@ static bool map_collect_record(int fd, __u32 key, struct 
record *rec)
                sum_dropped        += values[i].dropped;
                rec->cpu[i].info = values[i].info;
                sum_info        += values[i].info;
+               rec->cpu[i].err = values[i].err;
+               sum_err        += values[i].err;
        }
        rec->total.processed = sum_processed;
        rec->total.dropped   = sum_dropped;
        rec->total.info      = sum_info;
+       rec->total.err       = sum_err;
        return true;
 }
 
@@ -274,6 +279,18 @@ static double calc_info(struct datarec *r, struct datarec 
*p, double period)
        return pps;
 }
 
+static double calc_err(struct datarec *r, struct datarec *p, double period)
+{
+       __u64 packets = 0;
+       double pps = 0;
+
+       if (period > 0) {
+               packets = r->err - p->err;
+               pps = packets / period;
+       }
+       return pps;
+}
+
 static void stats_print(struct stats_record *stats_rec,
                        struct stats_record *stats_prev,
                        bool err_only)
@@ -412,11 +429,12 @@ static void stats_print(struct stats_record *stats_rec,
 
        /* devmap ndo_xdp_xmit stats */
        {
-               char *fmt1 = "%-15s %-7d %'-12.0f %'-12.0f %'-10.2f %s\n";
-               char *fmt2 = "%-15s %-7s %'-12.0f %'-12.0f %'-10.2f %s\n";
+               char *fmt1 = "%-15s %-7d %'-12.0f %'-12.0f %'-10.2f %s %s\n";
+               char *fmt2 = "%-15s %-7s %'-12.0f %'-12.0f %'-10.2f %s %s\n";
                struct record *rec, *prev;
-               double drop, info;
+               double drop, info, err;
                char *i_str = "";
+               char *err_str = "";
 
                rec  =  &stats_rec->xdp_devmap_xmit;
                prev = &stats_prev->xdp_devmap_xmit;
@@ -428,22 +446,29 @@ static void stats_print(struct stats_record *stats_rec,
                        pps  = calc_pps(r, p, t);
                        drop = calc_drop(r, p, t);
                        info = calc_info(r, p, t);
+                       err  = calc_err(r, p, t);
                        if (info > 0) {
                                i_str = "bulk-average";
                                info = (pps+drop) / info; /* calc avg bulk */
                        }
+                       if (err > 0)
+                               err_str = "drv-err";
                        if (pps > 0 || drop > 0)
                                printf(fmt1, "devmap-xmit",
-                                      i, pps, drop, info, i_str);
+                                      i, pps, drop, info, i_str, err_str);
                }
                pps = calc_pps(&rec->total, &prev->total, t);
                drop = calc_drop(&rec->total, &prev->total, t);
                info = calc_info(&rec->total, &prev->total, t);
+               err  = calc_err(&rec->total, &prev->total, t);
                if (info > 0) {
                        i_str = "bulk-average";
                        info = (pps+drop) / info; /* calc avg bulk */
                }
-               printf(fmt2, "devmap-xmit", "total", pps, drop, info, i_str);
+               if (err > 0)
+                       err_str = "drv-err";
+               printf(fmt2, "devmap-xmit", "total", pps, drop,
+                      info, i_str, err_str);
        }
 
        printf("\n");