bgpd: use bm buffer for rcvd_attr_str debug logging

[enkechen-panw]

The embedded rcvd_attr_str[BUFSIZ] array in struct peer consumes 8192 bytes per peer, but is only used for debug logging of received BGP UPDATE attributes.

Change to a bm buffer since BGP packet processing is single-threaded in the event loop. This eliminates 8KB of memory usage per peer.

[greptile-apps]

Greptile Summary

This PR optimizes memory usage by moving rcvd_attr_str[BUFSIZ] and rcvd_attr_printed from struct peer to the singleton struct bgp_master, saving 8 KB per peer. The change is safe under FRR's single-threaded BGP event loop, where only one UPDATE message is processed at a time.

• bgpd/bgpd.h: Removes the two fields from struct peer and adds them to struct bgp_master, with a comment noting the single-threaded assumption.
• bgpd/bgp_packet.c: Resets bm->rcvd_attr_str[0] = '\0' at the start of bgp_update_receive (replacing the previous full memset) and adds an explicit clear at the function's successful-exit path for defensive hygiene.
• bgpd/bgp_route.c: All three logging sites that checked peer->rcvd_attr_printed now also guard on bm->rcvd_attr_str[0] to prevent printing a stale empty string if bgp_dump_attr was never called for the current UPDATE.

Confidence Score: 5/5

The change is safe to merge — it eliminates per-peer heap bloat without altering any observable behavior under FRR's single-threaded BGP event loop.

All three files make consistent, mechanically straightforward substitutions of peer-scoped fields for the bm singleton. The reset at function entry, the guard added in bgp_route.c (bm->rcvd_attr_str[0]), and the defensive clear at the successful-return path together maintain identical semantics to the original code. No data is dropped, no logging path is silently suppressed, and the single-threaded processing model that makes the global buffer safe is well-established in FRR.

No files require special attention.

Important Files Changed

Filename	Overview
bgpd/bgpd.h	Moves rcvd_attr_str[BUFSIZ] and rcvd_attr_printed from struct peer to struct bgp_master; removes the old per-peer fields and their accompanying thread-safety warning comment.
bgpd/bgp_packet.c	Replaces memset-based reset with bm->rcvd_attr_str[0] = '\0' at start of bgp_update_receive, switches all attribute-string references to bm, and adds a defensive clear at the successful-return path.
bgpd/bgp_route.c	Updates three attribute-logging sites to use bm->rcvd_attr_printed and bm->rcvd_attr_str, adding a bm->rcvd_attr_str[0] guard to skip printing when the buffer has not been populated.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant EL as Event Loop (single thread)
    participant BPkt as bgp_packet.c
    participant BM as bgp_master (bm)
    participant BRt as bgp_route.c

    EL->>BPkt: bgp_update_receive()
    BPkt->>BM: "rcvd_attr_str[0] = '\0'"
    BPkt->>BM: "rcvd_attr_printed = false"
    BPkt->>BPkt: bgp_attr_parse()
    alt debug ON or parse error
        BPkt->>BM: bgp_dump_attr → rcvd_attr_str
        alt UPDATE_DETAIL debug
            BPkt->>BM: zlog_debug(rcvd_attr_str)
            BPkt->>BM: "rcvd_attr_printed = true"
        end
    end
    loop for each NLRI prefix
        BPkt->>BRt: bgp_nlri_parse → bgp_update()
        alt "debug ON && !rcvd_attr_printed && rcvd_attr_str[0]"
            BRt->>BM: zlog_debug(rcvd_attr_str)
            BRt->>BM: "rcvd_attr_printed = true"
        end
    end
    BPkt->>BM: "rcvd_attr_str[0] = '\0' (defensive clear)"
    BPkt->>EL: Receive_UPDATE_message

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sequenceDiagram
    participant EL as Event Loop (single thread)
    participant BPkt as bgp_packet.c
    participant BM as bgp_master (bm)
    participant BRt as bgp_route.c

    EL->>BPkt: bgp_update_receive()
    BPkt->>BM: "rcvd_attr_str[0] = '\0'"
    BPkt->>BM: "rcvd_attr_printed = false"
    BPkt->>BPkt: bgp_attr_parse()
    alt debug ON or parse error
        BPkt->>BM: bgp_dump_attr → rcvd_attr_str
        alt UPDATE_DETAIL debug
            BPkt->>BM: zlog_debug(rcvd_attr_str)
            BPkt->>BM: "rcvd_attr_printed = true"
        end
    end
    loop for each NLRI prefix
        BPkt->>BRt: bgp_nlri_parse → bgp_update()
        alt "debug ON && !rcvd_attr_printed && rcvd_attr_str[0]"
            BRt->>BM: zlog_debug(rcvd_attr_str)
            BRt->>BM: "rcvd_attr_printed = true"
        end
    end
    BPkt->>BM: "rcvd_attr_str[0] = '\0' (defensive clear)"
    BPkt->>EL: Receive_UPDATE_message

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_{Reviews (4): Last reviewed commit: "bgpd: use bm buffer for rcvd_attr_str de..." | Re-trigger Greptile}

[enkechen-panw]

@greptileai review

[enkechen-panw]

@greptileai review

[enkechen-panw]

@greptileai review

[riw777]

looks good