libbpf-tools: Fix misaligned pointer accesses in tcplife

The perf buffer in tcplife doesn't maintain 8 byte alignment
for saddr, daddr, ts_us, span_us, rx_b and tx_b in struct event.
 When building with "-fsanitize=alignment
 -fsanitize-trap=undefined" failures happen in handle_event.
Fix these by copying the event from the perf buffer before
accessing.

This is similar to a fix in exitsnoop where different ways to handle
misaligned pointers were discussed:
iovisor#4760

Signed-off-by: Ian Rogers <[email protected]>

libbpf-tools/tcplife.c

@@ -116,23 +116,30 @@ static void sig_int(int signo)
 static void handle_event(void *ctx, int cpu, void *data, __u32 data_sz)
 {
  char ts[32], saddr[48], daddr[48];
- struct event *e = data;
+ struct event e;
  struct tm *tm;
  time_t t;
 
+ if (data_sz < sizeof(e)) {
+ printf("Error: packet too small\n");
+ return;
+ }
+ /* Copy data as alignment in the perf buffer isn't guaranteed. */
+ memcpy(&e, data, sizeof(e));
+
  if (emit_timestamp) {
  time(&t);
  tm = localtime(&t);
  strftime(ts, sizeof(ts), "%H:%M:%S", tm);
  printf("%8s ", ts);
  }
 
- inet_ntop(e->family, &e->saddr, saddr, sizeof(saddr));
- inet_ntop(e->family, &e->daddr, daddr, sizeof(daddr));
+ inet_ntop(e.family, &e.saddr, saddr, sizeof(saddr));
+ inet_ntop(e.family, &e.daddr, daddr, sizeof(daddr));
 
  printf("%-7d %-16s %-*s %-5d %-*s %-5d %-6.2f %-6.2f %-.2f\n",
- e->pid, e->comm, column_width, saddr, e->sport, column_width, daddr, e->dport,
- (double)e->tx_b / 1024, (double)e->rx_b / 1024, (double)e->span_us / 1000);
+ e.pid, e.comm, column_width, saddr, e.sport, column_width, daddr, e.dport,
+ (double)e.tx_b / 1024, (double)e.rx_b / 1024, (double)e.span_us / 1000);
 }
 
 static void handle_lost_events(void *ctx, int cpu, __u64 lost_cnt)