gossip: fix gossip publishing invalid UDP datagrams

While the header_sz mcache sig is ignored by the XDP tile it is used by the socket tile. This commit also fixes consistently getting the socket tile in the standalone gossip topology.

Author: two-heart

src/app/firedancer-dev/commands/gossip.c

@@ -762,6 +762,7 @@ gossip_cmd_fn( args_t *   args,
   printf("Found %lu gossvf tiles\n", gossvf_tiles.tile_count);
 
   ulong net_tile_idx = fd_topo_find_tile( &config->topo, "net", 0UL );
+  if ( net_tile_idx==ULONG_MAX ) net_tile_idx = fd_topo_find_tile( &config->topo, "sock", 0UL );
   FD_TEST( net_tile_idx!=ULONG_MAX );
   fd_topo_tile_t * net_tile = &config->topo.tiles[ net_tile_idx ];
 

src/discof/gossip/fd_gossip_tile.c

@@ -62,7 +62,7 @@ gossip_send_fn( void *                ctx,
   fd_memcpy( packet+sizeof(fd_ip4_udp_hdrs_t), payload, payload_sz );
 
   ulong tspub     = fd_frag_meta_ts_comp( fd_tickcount() );
-  ulong sig       = fd_disco_netmux_sig( peer_address->addr, peer_address->port, peer_address->addr, DST_PROTO_OUTGOING, 0UL /* ignored */ );
+  ulong sig       = fd_disco_netmux_sig( peer_address->addr, peer_address->port, peer_address->addr, DST_PROTO_OUTGOING, sizeof(fd_ip4_udp_hdrs_t) );
   ulong packet_sz = payload_sz + sizeof(fd_ip4_udp_hdrs_t);
 
   fd_stem_publish( stem, gossip_ctx->net_out->idx, sig, gossip_ctx->net_out->chunk, packet_sz, 0UL, tspub, tsorig );