ss: output TCP BBR diag information

Dump useful TCP BBR state information from a struct tcp_bbr_info that
was grabbed using the inet_diag API.

We tolerate info that is shorter or longer than expected, in case the
kernel is older or newer than the ss binary. We simply print the
minimum of what is expected from the kernel and what is provided from
the kernel. We use the same trick as that used for struct tcp_info:
when the info from the kernel is shorter than we hoped, we pad the end
with zeroes, and don't print fields if they are zero.

The BBR output looks like:
  bbr:(bw:1.2Mbps,mrtt:18.965,pacing_gain:2.88672,cwnd_gain:2.88672)

The motivation here is to be consistent with DCTCP, which looks like:
  dctcp(ce_state:23,alpha:23,ab_ecn:23,ab_tot:23)

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>

diff --git a/misc/ss.c b/misc/ss.c
index 3b268d9994260e4af39c1ab6fb5c328e91c6c5e6..a36ad5af8fa4a9ea95c90386b0ad38de01582b2c 100644 (file)
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -788,6 +788,7 @@ struct tcpstat {
        bool                has_fastopen_opt;
        bool                has_wscale_opt;
        struct dctcpstat    *dctcp;
+       struct tcp_bbr_info *bbr_info;
 };
 
 static void sock_state_print(struct sockstat *s, const char *sock_name)
@@ -1783,6 +1784,25 @@ static void tcp_stats_print(struct tcpstat *s)
                printf(" dctcp:fallback_mode");
        }
 
+       if (s->bbr_info) {
+               __u64 bw;
+
+               bw = s->bbr_info->bbr_bw_hi;
+               bw <<= 32;
+               bw |= s->bbr_info->bbr_bw_lo;
+
+               printf(" bbr:(bw:%sbps,mrtt:%g",
+                      sprint_bw(b1, bw * 8.0),
+                      (double)s->bbr_info->bbr_min_rtt / 1000.0);
+               if (s->bbr_info->bbr_pacing_gain)
+                       printf(",pacing_gain:%g",
+                              (double)s->bbr_info->bbr_pacing_gain / 256.0);
+               if (s->bbr_info->bbr_cwnd_gain)
+                       printf(",cwnd_gain:%g",
+                              (double)s->bbr_info->bbr_cwnd_gain / 256.0);
+               printf(")");
+       }
+
        if (s->send_bps)
                printf(" send %sbps", sprint_bw(b1, s->send_bps));
        if (s->lastsnd)
@@ -2061,6 +2081,16 @@ static void tcp_show_info(const struct nlmsghdr *nlh, struct inet_diag_msg *r,
                        s.dctcp         = dctcp;
                }
 
+               if (tb[INET_DIAG_BBRINFO]) {
+                       const void *bbr_info = RTA_DATA(tb[INET_DIAG_BBRINFO]);
+                       int len = min(RTA_PAYLOAD(tb[INET_DIAG_BBRINFO]),
+                                     sizeof(*s.bbr_info));
+
+                       s.bbr_info = calloc(1, sizeof(*s.bbr_info));
+                       if (s.bbr_info && bbr_info)
+                               memcpy(s.bbr_info, bbr_info, len);
+               }
+
                if (rtt > 0 && info->tcpi_snd_mss && info->tcpi_snd_cwnd) {
                        s.send_bps = (double) info->tcpi_snd_cwnd *
                                (double)info->tcpi_snd_mss * 8000000. / rtt;
@@ -2085,6 +2115,7 @@ static void tcp_show_info(const struct nlmsghdr *nlh, struct inet_diag_msg *r,
                        s.min_rtt = (double) info->tcpi_min_rtt / 1000;
                tcp_stats_print(&s);
                free(s.dctcp);
+               free(s.bbr_info);
        }
 }