[Bridge] STP Explanation (2)

Stephen Hemminger shemminger at osdl.org
Fri Jul 1 10:51:47 PDT 2005


On Thu, 30 Jun 2005 12:51:59 +0200 (CEST)
shenry82 <shenry82 at voila.fr> wrote:

> I saw some big mistakes, here's the correct version :
> --------------------------------------------------------------------
> void br_send_config_bpdu(struct net_bridge_port *p, struct bpdu *bpdu)
> {
> 	unsigned char buf[42];
> 
> 	buf[0] = bpdu->bpdu_header.protocol[0]; //0x00
> 	buf[1] = bpdu->bpdu_header.protocol[1]; //0x00
> 	buf[2] = bpdu->bpdu_header.version; //0x02
> 	buf[3] = BPDU_TYPE_CONFIG;
> 	buf[4] = bpdu->bpdu_body.flags.topo_change;
> 	buf[5] = bpdu->bpdu_body.flags.proposal;
> 	buf[6] = bpdu->bpdu_body.flags.port_role[0];
> 	buf[7] = bpdu->bpdu_body.flags.port_role[1];
> 	buf[8] = bpdu->bpdu_body.flags.learning;
> 	buf[9] = bpdu->bpdu_body.flags.forwarding;
> 	buf[10] = bpdu->bpdu_body.flags.agreement;
> 	buf[11] = bpdu->bpdu_body.flags.topo_change_ack;	
> 	buf[12] = bpdu->bpdu_body.root_id.prio[0];
> 	buf[13] = bpdu->bpdu_body.root_id.prio[1];
> 	buf[14] = bpdu->bpdu_body.root_id.addr[0];
> 	buf[15] = bpdu->bpdu_body.root_id.addr[1];
> 	buf[16] = bpdu->bpdu_body.root_id.addr[2];
> 	buf[17] = bpdu->bpdu_body.root_id.addr[3];
> 	buf[18] = bpdu->bpdu_body.root_id.addr[4];
> 	buf[19] = bpdu->bpdu_body.root_id.addr[5];
> 	buf[20] = (bpdu->bpdu_body.root_path_cost >> 24) & 0xFF;
> 	buf[21] = (bpdu->bpdu_body.root_path_cost >> 16) & 0xFF;
> 	buf[22] = (bpdu->bpdu_body.root_path_cost >> 8) & 0xFF;
> 	buf[23] = bpdu->bpdu_body.root_path_cost & 0xFF;
> 	buf[24] = bpdu->bpdu_body.bridge_id.prio[0];
> 	buf[25] = bpdu->bpdu_body.bridge_id.prio[1];
> 	buf[26] = bpdu->bpdu_body.bridge_id.addr[0];
> 	buf[27] = bpdu->bpdu_body.bridge_id.addr[1];
> 	buf[28] = bpdu->bpdu_body.bridge_id.addr[2];
> 	buf[29] = bpdu->bpdu_body.bridge_id.addr[3];
> 	buf[30] = bpdu->bpdu_body.bridge_id.addr[4];
> 	buf[31] = bpdu->bpdu_body.bridge_id.addr[5];
> 	buf[32] = (bpdu->bpdu_body.port_id >> 8) & 0xFF;
> 	buf[33] = bpdu->bpdu_body.port_id & 0xFF;
> 
> 	br_set_ticks(buf+34, bpdu->bpdu_body.message_age);
> 	br_set_ticks(buf+36, bpdu->bpdu_body.max_age);
> 	br_set_ticks(buf+38, bpdu->bpdu_body.hello_time);
> 	br_set_ticks(buf+40, bpdu->bpdu_body.forward_delay);
> 
> 	br_send_bpdu(p, buf, 42);
> }
> -------------------------------------------------------------------------
> I also modified the following function like this :
> ------------------------------------------------------------------------------
> /* called under bridge lock */
> void br_send_tcn_bpdu(struct net_bridge_port *p)
> {
> 	unsigned char buf[4];
> 
> 	buf[0] = bpdu->bpdu_header.protocol[0]; //0x00
> 	buf[1] = bpdu->bpdu_header.protocol[1]; //0x00
> 	buf[2] = bpdu->bpdu_header.version; //0x02
> 	buf[3] = BPDU_TYPE_TCN;
> 	br_send_bpdu(p, buf, 4);
> }
> 
> static unsigned char header[3] = {0x00, 0x00, 0x02};
> ------------------------------------------------------------------------
> 
> please tell me what do you think of because if i'm getting the wrong way, i prefer to know it quickly. ^^
> 

This matches the style of the existing code, but I really don't like that style.
I would prefer to rework that code to define the STP protocol header as a structure
and overlay structure on an skb.  More like the existing IP code does.  



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