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samples/bpf: xdp_monitor also record xdp_exception tracepoint
Also monitor the tracepoint xdp_exception. This tracepoint is usually invoked by the drivers. Programs themselves can activate this by returning XDP_ABORTED, which will drop the packet but also trigger the tracepoint. This is useful for distinguishing intentional (XDP_DROP) vs. ebpf-program error cases that cased a drop (XDP_ABORTED). Drivers also use this tracepoint for reporting on XDP actions that are unknown to the specific driver. This can help the user to detect if a driver e.g. doesn't implement XDP_REDIRECT yet. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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+121
-25
lines changed

2 files changed

+121
-25
lines changed

‎samples/bpf/xdp_monitor_kern.c

Lines changed: 37 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,6 +13,14 @@ struct bpf_map_def SEC("maps") redirect_err_cnt = {
1313
/* TODO: have entries for all possible errno's */
1414
};
1515

16+
#define XDP_UNKNOWN XDP_REDIRECT + 1
17+
struct bpf_map_def SEC("maps") exception_cnt = {
18+
.type = BPF_MAP_TYPE_PERCPU_ARRAY,
19+
.key_size = sizeof(u32),
20+
.value_size = sizeof(u64),
21+
.max_entries = XDP_UNKNOWN + 1,
22+
};
23+
1624
/* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format
1725
* Code in: kernel/include/trace/events/xdp.h
1826
*/
@@ -44,7 +52,7 @@ int xdp_redirect_collect_stat(struct xdp_redirect_ctx *ctx)
4452

4553
cnt = bpf_map_lookup_elem(&redirect_err_cnt, &key);
4654
if (!cnt)
47-
return 0;
55+
return 1;
4856
*cnt += 1;
4957

5058
return 0; /* Indicate event was filtered (no further processing)*/
@@ -82,3 +90,31 @@ int trace_xdp_redirect_map(struct xdp_redirect_ctx *ctx)
8290
{
8391
return xdp_redirect_collect_stat(ctx);
8492
}
93+
94+
/* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_exception/format
95+
* Code in: kernel/include/trace/events/xdp.h
96+
*/
97+
struct xdp_exception_ctx {
98+
u64 __pad; // First 8 bytes are not accessible by bpf code
99+
int prog_id; // offset:8; size:4; signed:1;
100+
u32 act; // offset:12; size:4; signed:0;
101+
int ifindex; // offset:16; size:4; signed:1;
102+
};
103+
104+
SEC("tracepoint/xdp/xdp_exception")
105+
int trace_xdp_exception(struct xdp_exception_ctx *ctx)
106+
{
107+
u64 *cnt;;
108+
u32 key;
109+
110+
key = ctx->act;
111+
if (key > XDP_REDIRECT)
112+
key = XDP_UNKNOWN;
113+
114+
cnt = bpf_map_lookup_elem(&exception_cnt, &key);
115+
if (!cnt)
116+
return 1;
117+
*cnt += 1;
118+
119+
return 0;
120+
}

‎samples/bpf/xdp_monitor_user.c

Lines changed: 84 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -89,6 +89,23 @@ static const char *err2str(int err)
8989
return redir_names[err];
9090
return NULL;
9191
}
92+
/* enum xdp_action */
93+
#define XDP_UNKNOWN XDP_REDIRECT + 1
94+
#define XDP_ACTION_MAX (XDP_UNKNOWN + 1)
95+
static const char *xdp_action_names[XDP_ACTION_MAX] = {
96+
[XDP_ABORTED] = "XDP_ABORTED",
97+
[XDP_DROP] = "XDP_DROP",
98+
[XDP_PASS] = "XDP_PASS",
99+
[XDP_TX] = "XDP_TX",
100+
[XDP_REDIRECT] = "XDP_REDIRECT",
101+
[XDP_UNKNOWN] = "XDP_UNKNOWN",
102+
};
103+
static const char *action2str(int action)
104+
{
105+
if (action < XDP_ACTION_MAX)
106+
return xdp_action_names[action];
107+
return NULL;
108+
}
92109

93110
struct record {
94111
__u64 counter;
@@ -97,46 +114,80 @@ struct record {
97114

98115
struct stats_record {
99116
struct record xdp_redir[REDIR_RES_MAX];
117+
struct record xdp_exception[XDP_ACTION_MAX];
100118
};
101119

102120
static void stats_print_headers(bool err_only)
103121
{
104122
if (err_only)
105123
printf("\n%s\n", __doc_err_only__);
106124

107-
printf("%-14s %-10s %-18s %-9s\n",
108-
"XDP_REDIRECT", "pps ", "pps-human-readable", "measure-period");
125+
printf("%-14s %-11s %-10s %-18s %-9s\n",
126+
"ACTION", "result", "pps ", "pps-human-readable", "measure-period");
127+
}
128+
129+
static double calc_period(struct record *r, struct record *p)
130+
{
131+
double period_ = 0;
132+
__u64 period = 0;
133+
134+
period = r->timestamp - p->timestamp;
135+
if (period > 0)
136+
period_ = ((double) period / NANOSEC_PER_SEC);
137+
138+
return period_;
139+
}
140+
141+
static double calc_pps(struct record *r, struct record *p, double period)
142+
{
143+
__u64 packets = 0;
144+
double pps = 0;
145+
146+
if (period > 0) {
147+
packets = r->counter - p->counter;
148+
pps = packets / period;
149+
}
150+
return pps;
109151
}
110152

111153
static void stats_print(struct stats_record *rec,
112154
struct stats_record *prev,
113155
bool err_only)
114156
{
157+
double period = 0, pps = 0;
158+
struct record *r, *p;
115159
int i = 0;
116160

161+
char *fmt = "%-14s %-11s %-10.0f %'-18.0f %f\n";
162+
163+
/* tracepoint: xdp:xdp_redirect_* */
117164
if (err_only)
118165
i = REDIR_ERROR;
119166

120167
for (; i < REDIR_RES_MAX; i++) {
121-
struct record *r = &rec->xdp_redir[i];
122-
struct record *p = &prev->xdp_redir[i];
123-
__u64 period = 0;
124-
__u64 packets = 0;
125-
double pps = 0;
126-
double period_ = 0;
168+
r = &rec->xdp_redir[i];
169+
p = &prev->xdp_redir[i];
127170

128171
if (p->timestamp) {
129-
packets = r->counter - p->counter;
130-
period = r->timestamp - p->timestamp;
131-
if (period > 0) {
132-
period_ = ((double) period / NANOSEC_PER_SEC);
133-
pps = packets / period_;
134-
}
172+
period = calc_period(r, p);
173+
pps = calc_pps(r, p, period);
135174
}
175+
printf(fmt, "XDP_REDIRECT", err2str(i), pps, pps, period);
176+
}
136177

137-
printf("%-14s %-10.0f %'-18.0f %f\n",
138-
err2str(i), pps, pps, period_);
178+
/* tracepoint: xdp:xdp_exception */
179+
for (i = 0; i < XDP_ACTION_MAX; i++) {
180+
r = &rec->xdp_exception[i];
181+
p = &prev->xdp_exception[i];
182+
if (p->timestamp) {
183+
period = calc_period(r, p);
184+
pps = calc_pps(r, p, period);
185+
}
186+
if (pps > 0)
187+
printf(fmt, action2str(i), "Exception",
188+
pps, pps, period);
139189
}
190+
printf("\n");
140191
}
141192

142193
static __u64 get_key32_value64_percpu(int fd, __u32 key)
@@ -160,25 +211,33 @@ static __u64 get_key32_value64_percpu(int fd, __u32 key)
160211
return sum;
161212
}
162213

163-
static bool stats_collect(int fd, struct stats_record *rec)
214+
static bool stats_collect(struct stats_record *rec)
164215
{
216+
int fd;
165217
int i;
166218

167219
/* TODO: Detect if someone unloaded the perf event_fd's, as
168220
* this can happen by someone running perf-record -e
169221
*/
170222

223+
fd = map_data[0].fd; /* map0: redirect_err_cnt */
171224
for (i = 0; i < REDIR_RES_MAX; i++) {
172225
rec->xdp_redir[i].timestamp = gettime();
173226
rec->xdp_redir[i].counter = get_key32_value64_percpu(fd, i);
174227
}
228+
229+
fd = map_data[1].fd; /* map1: exception_cnt */
230+
for (i = 0; i < XDP_ACTION_MAX; i++) {
231+
rec->xdp_exception[i].timestamp = gettime();
232+
rec->xdp_exception[i].counter = get_key32_value64_percpu(fd, i);
233+
}
234+
175235
return true;
176236
}
177237

178238
static void stats_poll(int interval, bool err_only)
179239
{
180240
struct stats_record rec, prev;
181-
int map_fd;
182241

183242
memset(&rec, 0, sizeof(rec));
184243

@@ -190,16 +249,17 @@ static void stats_poll(int interval, bool err_only)
190249
printf("\n%s", __doc__);
191250

192251
/* TODO Need more advanced stats on error types */
193-
if (verbose)
194-
printf(" - Stats map: %s\n", map_data[0].name);
195-
map_fd = map_data[0].fd;
196-
197-
stats_print_headers(err_only);
252+
if (verbose) {
253+
printf(" - Stats map0: %s\n", map_data[0].name);
254+
printf(" - Stats map1: %s\n", map_data[1].name);
255+
printf("\n");
256+
}
198257
fflush(stdout);
199258

200259
while (1) {
201260
memcpy(&prev, &rec, sizeof(rec));
202-
stats_collect(map_fd, &rec);
261+
stats_collect(&rec);
262+
stats_print_headers(err_only);
203263
stats_print(&rec, &prev, err_only);
204264
fflush(stdout);
205265
sleep(interval);

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