83 lines
1.5 KiB
C
Executable file
83 lines
1.5 KiB
C
Executable file
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/* GRE flag bits */
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enum {
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GRE_chksum = (1<<15),
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GRE_routing = (1<<14),
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GRE_key = (1<<13),
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GRE_seq = (1<<12),
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GRE_srcrt = (1<<11),
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GRE_recur = (7<<8),
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GRE_ack = (1<<7),
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GRE_ver = 0x7,
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};
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/* GRE protocols */
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enum {
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GRE_sna = 0x0004,
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GRE_osi = 0x00fe,
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GRE_pup = 0x0200,
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GRE_xns = 0x0600,
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GRE_ip = 0x0800,
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GRE_chaos = 0x0804,
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GRE_rfc826 = 0x0806,
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GRE_frarp = 0x0808,
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GRE_vines = 0x0bad,
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GRE_vinesecho = 0x0bae,
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GRE_vinesloop = 0x0baf,
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GRE_decnetIV = 0x6003,
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GRE_ppp = 0x880b,
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};
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int
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sprintgre(void *a, char *buf, int len)
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{
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int flag, prot, chksum, offset, key, seq, ack;
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int n;
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uchar *p = a;
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chksum = offset = key = seq = ack = 0;
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flag = NetS(p);
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prot = NetS(p+2);
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p += 4; len -= 4;
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if(flag & (GRE_chksum|GRE_routing)){
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chksum = NetS(p);
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offset = NetS(p+2);
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p += 4; len -= 4;
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}
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if(flag&GRE_key){
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key = NetL(p);
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p += 4; len -= 4;
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}
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if(flag&GRE_seq){
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seq = NetL(p);
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p += 4; len -= 4;
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}
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if(flag&GRE_ack){
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ack = NetL(p);
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p += 4; len -= 4;
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}
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/* skip routing if present */
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if(flag&GRE_routing) {
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while(len >= 4 && (n=p[3]) != 0) {
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len -= n;
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p += n;
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}
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}
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USED(offset);
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USED(chksum);
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n = sprint(buf, "GRE(f %4.4ux p %ux k %ux", flag, prot, key);
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if(flag&GRE_seq)
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n += sprint(buf+n, " s %ux", seq);
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if(flag&GRE_ack)
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n += sprint(buf+n, " a %ux", ack);
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n += sprint(buf+n, " len = %d/%d) ", len, key>>16);
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if(prot == GRE_ppp && len > 0)
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n += sprintppp(p, buf+n, len);
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else
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n += sprintx(p, buf+n, len);
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return n;
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}
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