zebra: simplify FPM buffer full detection

Remove code duplication and document hardcoded values.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

diff --git a/zebra/dplane_fpm_nl.c b/zebra/dplane_fpm_nl.c
index d59c75a1a001d6355055740bc7f9ad6e6311dadd..6dae1756a72f460be0678e72ac6fec695c7fc322 100644 (file)
--- a/zebra/dplane_fpm_nl.c
+++ b/zebra/dplane_fpm_nl.c
@@ -47,6 +47,19 @@
 #define SOUTHBOUND_DEFAULT_ADDR INADDR_LOOPBACK
 #define SOUTHBOUND_DEFAULT_PORT 2620
 
+/**
+ * FPM header:
+ * {
+ *   version: 1 byte (always 1),
+ *   type: 1 byte (1 for netlink, 2 protobuf),
+ *   len: 2 bytes (network order),
+ * }
+ *
+ * This header is used with any format to tell the users how many bytes to
+ * expect.
+ */
+#define FPM_HEADER_SIZE 4
+
 static const char *prov_name = "dplane_fpm_nl";
 
 struct fpm_nl_ctx {
@@ -545,13 +558,6 @@ static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx)
                }
 
                nl_buf_len = (size_t)rv;
-               if (STREAM_WRITEABLE(fnc->obuf) < nl_buf_len) {
-                       fnc->counters.buffer_full++;
-                       zlog_debug("%s: not enough output buffer (%ld vs %lu)",
-                                  __func__, STREAM_WRITEABLE(fnc->obuf),
-                                  nl_buf_len);
-                       return -1;
-               }
 
                /* UPDATE operations need a INSTALL, otherwise just quit. */
                if (dplane_ctx_get_op(ctx) == DPLANE_OP_ROUTE_DELETE)
@@ -569,13 +575,6 @@ static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx)
                }
 
                nl_buf_len += (size_t)rv;
-               if (STREAM_WRITEABLE(fnc->obuf) < nl_buf_len) {
-                       fnc->counters.buffer_full++;
-                       zlog_debug("%s: not enough output buffer (%ld vs %lu)",
-                                  __func__, STREAM_WRITEABLE(fnc->obuf),
-                                  nl_buf_len);
-                       return -1;
-               }
                break;
 
        case DPLANE_OP_MAC_INSTALL:
@@ -588,13 +587,6 @@ static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx)
                }
 
                nl_buf_len = (size_t)rv;
-               if (STREAM_WRITEABLE(fnc->obuf) < nl_buf_len) {
-                       fnc->counters.buffer_full++;
-                       zlog_debug("%s: not enough output buffer (%ld vs %lu)",
-                                  __func__, STREAM_WRITEABLE(fnc->obuf),
-                                  nl_buf_len);
-                       return -1;
-               }
                break;
 
        case DPLANE_OP_NH_INSTALL:
@@ -630,18 +622,26 @@ static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx)
        if (nl_buf_len == 0)
                return 0;
 
+       /* We must know if someday a message goes beyond 65KiB. */
+       assert((nl_buf_len + FPM_HEADER_SIZE) <= UINT16_MAX);
+
+       /* Check if we have enough buffer space. */
+       if (STREAM_WRITEABLE(fnc->obuf) < (nl_buf_len + FPM_HEADER_SIZE)) {
+               fnc->counters.buffer_full++;
+               zlog_debug("%s: buffer full: wants to write %lu but has %ld",
+                          __func__, nl_buf_len + FPM_HEADER_SIZE,
+                          STREAM_WRITEABLE(fnc->obuf));
+               return -1;
+       }
+
        /*
-        * FPM header:
-        * {
-        *   version: 1 byte (always 1),
-        *   type: 1 byte (1 for netlink, 2 protobuf),
-        *   len: 2 bytes (network order),
-        * }
+        * Fill in the FPM header information.
+        *
+        * See FPM_HEADER_SIZE definition for more information.
         */
        stream_putc(fnc->obuf, 1);
        stream_putc(fnc->obuf, 1);
-       assert(nl_buf_len < UINT16_MAX);
-       stream_putw(fnc->obuf, nl_buf_len + 4);
+       stream_putw(fnc->obuf, nl_buf_len + FPM_HEADER_SIZE);
 
        /* Write current data. */
        stream_write(fnc->obuf, nl_buf, (size_t)nl_buf_len);
@@ -690,9 +690,6 @@ static int fpm_rib_send(struct thread *t)
                                /* Free the temporary allocated context. */
                                dplane_ctx_fini(&ctx);
 
-                               fnc->counters.buffer_full++;
-                               zlog_debug("%s: buffer full, come back later",
-                                          __func__);
                                thread_add_timer(zrouter.master, fpm_rib_send,
                                                 fnc, 1, &fnc->t_ribwalk);
                                return 0;
@@ -746,9 +743,6 @@ static void fpm_enqueue_rmac_table(struct hash_backet *backet, void *arg)
                        zif->brslave_info.br_if, vid, &zrmac->macaddr,
                        zrmac->fwd_info.r_vtep_ip, sticky);
        if (fpm_nl_enqueue(fra->fnc, fra->ctx) == -1) {
-               fra->fnc->counters.buffer_full++;
-               zlog_debug("%s: buffer full, come back later",
-                          __func__);
                thread_add_timer(zrouter.master, fpm_rmac_send,
                                 fra->fnc, 1, &fra->fnc->t_rmacwalk);
        }