tsnap.c - plan9port - [fork] Plan 9 from user space
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       ---
       tsnap.c (1521B)
       ---
            1 /*
            2  * SNAP.
            3  */
            4 
            5 #include <u.h>
            6 #include <libc.h>
            7 #include <ip.h>
            8 #include "dat.h"
            9 #include "protos.h"
           10 
           11 enum
           12 {
           13         Oorg,
           14         Oet,
           15 
           16         OuiEther = 0,
           17         OuiCisco = 0xc,
           18         OuiCisco90 = 0xf8,
           19         OuiRfc2684 = 0x80c2,
           20         OuiAppletalk = 0x80007,
           21 };
           22 
           23 static Mux p_mux[] =
           24 {
           25         {"ip",                0x0800,        } ,
           26         {"arp",                0x0806,        } ,
           27         {"rarp",        0x0806,        } ,
           28         {"ip6",         0x86dd, } ,
           29         {"pppoe_disc",        0x8863, },
           30         {"pppoe_sess",        0x8864, },
           31         {"eapol",        0x888e, },
           32         { 0 }
           33 };
           34 
           35 typedef struct Hdr Hdr;
           36 struct Hdr
           37 {
           38         uchar org[3];
           39         uchar et[2];
           40 };
           41 
           42 static Field p_fields[] =
           43 {
           44         { "org",        Fnum,        Oorg,        "org" },
           45         { "et",        Fnum,        Oet,        "et" },
           46         { 0 }
           47 };
           48 
           49 static void
           50 p_compile(Filter *f)
           51 {
           52         Mux *m;
           53 
           54         if(f->op == '='){
           55                 compile_cmp(snap.name, f, p_fields);
           56                 return;
           57         }
           58         for(m = p_mux; m->name != nil; m++){
           59                 if(strcmp(f->s, m->name) == 0){
           60                         f->pr = m->pr;
           61                         f->ulv = m->val;
           62                         f->subop = Oet;
           63                         return;
           64                 }
           65         }
           66         sysfatal("unknown snap field or protocol: %s", f->s);
           67 }
           68 
           69 static int
           70 p_filter(Filter *f, Msg *m)
           71 {
           72         Hdr *h;
           73 
           74         if(m->pe - m->ps < sizeof(Hdr))
           75                 return 0;
           76         h = (Hdr*)m->ps;
           77         m->ps += 5;
           78         switch(f->subop){
           79         case Oorg:
           80                 return f->ulv == Net3(h->org);
           81         case Oet:
           82                 return f->ulv == NetS(h->et);
           83         }
           84         return 0;
           85 }
           86 
           87 static int
           88 p_seprint(Msg *m)
           89 {
           90         Hdr *h;
           91 
           92         if(m->pe - m->ps < sizeof(Hdr))
           93                 return 0;
           94         h = (Hdr*)m->ps;
           95         m->ps += 5;
           96         demux(p_mux, NetS(h->et), NetS(h->et), m, &dump);
           97 
           98         m->p = seprint(m->p, m->e, "org=%06x et=%04x", Net3(h->org), NetS(h->et));
           99         return 0;
          100 }
          101 
          102 Proto snap =
          103 {
          104         "snap",
          105         p_compile,
          106         p_filter,
          107         p_seprint,
          108         p_mux,
          109         nil,
          110         nil,
          111         defaultframer
          112 };