trtcp.c - plan9port - [fork] Plan 9 from user space
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       trtcp.c (1859B)
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            1 #include <u.h>
            2 #include <libc.h>
            3 #include <ip.h>
            4 #include "dat.h"
            5 #include "protos.h"
            6 
            7 typedef struct Hdr Hdr;
            8 struct Hdr {
            9         uchar        hdr;                        /* RTCP header */
           10         uchar        pt;                        /* Packet type */
           11         uchar        len[2];                /* Report length */
           12         uchar        ssrc[4];                /* Synchronization source identifier */
           13         uchar        ntp[8];                /* NTP time stamp */
           14         uchar        rtp[4];                /* RTP time stamp */
           15         uchar        pktc[4];                /* Sender's packet count */
           16         uchar        octc[4];                /* Sender's octect count */
           17 };
           18 
           19 typedef struct Report Report;
           20 struct Report {
           21         uchar        ssrc[4];                /* SSRC identifier */
           22         uchar        lost[4];                /* Fraction + cumu lost */
           23         uchar        seqhi[4];                /* Highest seq number received */
           24         uchar        jitter[4];                /* Interarrival jitter */
           25         uchar        lsr[4];                /* Last SR */
           26         uchar        dlsr[4];                /* Delay since last SR */
           27 };
           28 
           29 enum{
           30         RTCPLEN = 28,                /* Minimum size of an RTCP header */
           31         REPORTLEN = 24
           32 };
           33 
           34 static int
           35 p_seprint(Msg *m)
           36 {
           37         Hdr*h;
           38         Report*r;
           39         int rc, i, frac;
           40         float dlsr;
           41 
           42         if(m->pe - m->ps < RTCPLEN)
           43                 return -1;
           44 
           45         h = (Hdr*)m->ps;
           46         if(m->pe - m->ps < (NetS(h->len) + 1) * 4)
           47                 return -1;
           48 
           49         rc = h->hdr & 0x1f;
           50         m->ps += RTCPLEN;
           51         m->p = seprint(m->p, m->e, "version=%d rc=%d tp=%d ssrc=%8ux ntp=%d.%.10ud rtp=%d pktc=%d octc=%d hlen=%d",
           52                                 (h->hdr >> 6) & 3, rc, h->pt, NetL(h->ssrc),
           53                                 NetL(h->ntp), (uint)NetL(&h->ntp[4]), NetL(h->rtp),
           54                                 NetL(h->pktc), NetL(h->octc),
           55                                 (NetS(h->len) + 1) * 4);
           56 
           57         for(i = 0; i < rc; i++){
           58                 r = (Report*)m->ps;
           59                 m->ps += REPORTLEN;
           60 
           61                 frac = (int)(((float)r->lost[0] * 100.) / 256.);
           62                 r->lost[0] = 0;
           63                 dlsr = (float)NetL(r->dlsr) / 65536.;
           64 
           65                 m->p = seprint(m->p, m->e, "\n\trr(csrc=%8ux frac=%3d%% cumu=%10d seqhi=%10ud jitter=%10d lsr=%8ux dlsr=%f)",
           66                                 NetL(r->ssrc), frac, NetL(r->lost), NetL(r->seqhi),
           67                                 NetL(r->jitter), NetL(r->lsr),
           68                                 dlsr);
           69         }
           70         m->pr = nil;
           71         return 0;
           72 }
           73 
           74 Proto rtcp = {
           75         "rtcp",
           76         nil,
           77         nil,
           78         p_seprint,
           79         nil,
           80         nil,
           81         nil,
           82         defaultframer
           83 };