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trap: deliver reserved multicast to the CPU by trap, STP first

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A reserved-multicast trap goes to the port named in EXT_CPU_CTRL, which
names no port out of reset, so trapped frames were dropped at ingress.
trap_init() points it at the CPU port once at startup, and
trap_rma_set() changes only the action field of an RMA register.

A trapped frame arrives without the VLAN tag a forwarded one gets, so
TRAP_RX_BODY() gives the offset of the payload for both forms.

STP now traps its address while it runs instead of steering it with a
static L2 entry per VLAN, so turning it on no longer walks the VLAN
table and a pvid change no longer needs stp off and on. With STP off
the flooding entries are restored as before.

A trapped BPDU passes the tagged-only ingress filter that drops a
forwarded one, so the stp_setup() warning about such ports goes.
This commit is contained in:
DrDoof authored and d00f committed 2026-10-12 01:16:28 +02:00
1 parent 84d9408151
commit 14b2ce1c49
8 files changed
+97 -48
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rtl837x_stp.c
+17 -21
View File
@@ -12,6 +12,7 @@
#include "rtl837x_regs.h"
#include "rtl837x_stp.h"
#include "rtl837x_port.h"
#include "rtl837x_trap.h"
#include "uip.h"
#include "machine.h"
@@ -85,6 +86,7 @@ __xdata uint16_t stp_link_now;
__xdata uint8_t stp_scratch;
__xdata uint8_t stp_tx_flags_extra; /* one-shot flags OR-ed into the next BPDU (TCA) */
__xdata uint8_t stp_rxbody;
__xdata uint16_t stp_rxlen; /* received frame length, saved before uip_len is consumed */
__xdata uint8_t stp_msg_age; /* message age of the root info we hold, seconds */
__xdata uint16_t stp_tc_while; /* ticks left to set the TC flag in our BPDUs */
@@ -121,11 +123,13 @@ struct stp_pkt {
uint8_t version1_length; /* RST BPDU only: length of the (empty) v1 part */
};
struct stp_pkt_in {
struct stp_pkt_in_hdr {
uint8_t stp_addr[6];
uint8_t src_addr[6];
struct rtl_tag rtl_tag;
struct vlan_tag vlan_tag;
};
struct stp_pkt_in {
uint16_t msg_len;
uint8_t dsap;
uint8_t ssap;
@@ -147,7 +151,8 @@ struct stp_pkt_in {
};
#define STP_O ((__xdata struct stp_pkt *)&uip_buf[RTL_FRAME_DESC_SIZE])
#define STP_I ((__xdata struct stp_pkt_in *)&uip_buf[0])
#define STP_H ((__xdata struct stp_pkt_in_hdr *)&uip_buf[0])
#define STP_I ((__xdata struct stp_pkt_in *)&uip_buf[stp_rxbody])
#define BPDU_VER_STP 0x00
#define BPDU_VER_RSTP 0x02
@@ -158,7 +163,8 @@ struct stp_pkt_in {
#define BPDU_LEN_CONFIG 0x26 // LLC and a 35 byte body
#define BPDU_LEN_RST 0x27 // LLC and a 36 byte body
#define BPDU_LEN_MIN_HEADER 33 // addresses through bpdu_type
#define BPDU_LEN_MIN_BODY 9
#define BPDU_LEN_FULL_BODY 40
#define BPDU_FLAG_TC 0x01
#define BPDU_FLAG_LEARNING 0x10
@@ -547,7 +553,8 @@ void stp_in(void) __banked
{
uint8_t port;
if (uip_len < BPDU_LEN_MIN_HEADER) {
stp_rxbody = TRAP_RX_BODY();
if (uip_len < stp_rxbody + BPDU_LEN_MIN_BODY) {
uip_len = 0;
return;
}
@@ -557,7 +564,7 @@ void stp_in(void) __banked
uip_len = 0;
/* Ingress port: low nibble of the CPU tag's pmask on RX */
stp_scratch = ((uint8_t)HTONS(STP_I->rtl_tag.pmask)) & 0x0f;
stp_scratch = ((uint8_t)HTONS(STP_H->rtl_tag.pmask)) & 0x0f;
if (stp_scratch < machine.min_port || stp_scratch > machine.max_port)
return;
port = stp_ent_of[stp_scratch];
@@ -607,7 +614,7 @@ void stp_in(void) __banked
}
/* Everything below reads the full Config/RST body. */
if (stp_rxlen < 64)
if (stp_rxlen < stp_rxbody + BPDU_LEN_FULL_BODY)
return;
/* Our own BPDU coming back: two of our ports sit on one segment. Only
@@ -865,8 +872,7 @@ void stp_defaults(void) __banked
/*
* Steer BPDUs while STP runs, and restore flooding when it stops.
* Changing a port's PVID while STP runs needs "stp off" then "stp on".
* Restore BPDU flooding when STP stops.
*/
static void stp_fdb_update(__xdata uint16_t pmask)
{
@@ -928,16 +934,6 @@ void stp_setup(void) __banked
print_reg(RTL837X_MSTP_STATES); write_char('\n');
for (stp_i = machine.min_port; stp_i <= machine.max_port; stp_i++) {
if (!(stp_pflags[stp_i] & STP_PF_ENABLED))
continue;
if (port_ingress_filter_get(stp_i) != VLAN_TAGGED)
continue;
print_string("STP: port ");
write_char('0' + machine.log_to_phys_port[stp_i]);
print_string(" admits tagged frames only - BPDUs are untagged and will not arrive\n");
}
/* Seed the carrier bitmap, so turning STP on does not report every
* port that was already down as a fresh topology change. */
reg_read_m(RTL837X_REG_LINKS_STS);
@@ -949,8 +945,7 @@ void stp_setup(void) __banked
stp_claim_root();
/* Take BPDUs to the CPU only - we are a participating bridge now. */
stp_fdb_update(PMASK_CPU);
trap_rma_set(RTL837X_RMA0_CONF, RTL837X_RMA_ACT_TRAP);
}
@@ -972,6 +967,7 @@ void stp_off(void) __banked
/* Restore BPDU transparency: flood them again like an unmanaged switch. */
stp_fdb_update(PMASK_CPU | (machine_detected.isRTL8373 ? PMASK_9 : PMASK_6));
trap_rma_set(RTL837X_RMA0_CONF, RTL837X_RMA_ACT_FORWARD);
}