Thanks Maxim,
On Thu, 8 Jun 2023 at 13:14, Maxim Uvarov maxim.uvarov@linaro.org wrote:
Ilias asked to make more clear results to compare the original stack and LWIP stack. So the difference between the current U-boot stack and the LWIP stack with 3 network commands is: a) 18Kb - ls -lh size b) 15Kb - bloat-o-meter script total line report.
BOM=linux/scripts/bloat-o-meter (script)
- 893K - U-boot CMD_NET=n
- 928K - U-boot CMD_NET=y TFTP=y PING=y WGET=y
BOM 1-2: Total: Before=692286, After=722283, chg +4.33% 3. 940K - U-boot CMD_NET=n, LWIP_TFTP=y LWIP_PING=y LWIP_PING=y BOM 1-3: Total: Before=692286, After=738425, chg +6.66%
That's much more readable! I discussed this with Tom over IRC and the size difference is certainly a reasonable trade-off for the extra functionality.
Can you tidy up the series and include DHCP and PXE done through LWIP?
Thanks /Ilias
BOM 2-3:
add/remove: 287/203 grow/shrink: 3/11 up/down: 43459/-27317 (16142) Function old new delta tcp_input - 3588 +3588 tcp_receive - 2884 +2884 ip4_reass - 1760 +1760 tcp_output - 1400 +1400 tcp_write - 1300 +1300 tcp_slowtmr - 1172 +1172 httpc_tcp_recv - 1044 +1044 tftp_recv - 888 +888 ip4_input - 700 +700 ip4_frag - 632 +632 icmp_input - 604 +604 udp_input - 596 +596 etharp_input - 512 +512 tcp_split_unsent_seg - 500 +500 ip4addr_aton - 492 +492 tcp_alloc - 484 +484 ip4_output_if_src - 476 +476 tcp_close_shutdown - 448 +448 etharp_query - 436 +436 httpc_init_connection_common.constprop - 416 +416 udp_sendto_if_src - 408 +408 etharp_output - 404 +404 arp_table - 400 +400 tcp_connect - 396 +396 pbuf_alloc - 376 +376 etharp_find_entry - 372 +372 tcp_abandon - 368 +368 tcp_zero_window_probe - 356 +356 raw_sendto_if_src - 328 +328 pbuf_copy_partial_pbuf - 328 +328 ip_reass_free_complete_datagram - 328 +328 tcp_create_segment - 300 +300 raw_input - 292 +292 uboot_lwip_init - 284 +284 ethernet_input - 284 +284 etharp_raw - 284 +284 tcp_output_alloc_header_common.constprop - 280 +280 cmds - 280 +280 udp_bind - 276 +276 tcp_oos_insert_segment - 276 +276 ip_reass_remove_oldest_datagram - 272 +272 icmp_send_response - 268 +268 netif_add - 260 +260 ping_send - 244 +244 tcp_rexmit - 232 +232 tcp_parseopt - 220 +220 tcp_free_acked_segments.constprop - 220 +220 send_request - 220 +220 inet_chksum_pseudo - 216 +216 ip4addr_ntoa_r - 212 +212 do_lwip_ping - 212 +212 tcp_enqueue_flags - 208 +208 etharp_output_to_arp_index - 208 +208 netif_set_addr - 204 +204 tcp_fasttmr - 200 +200 tcp_rexmit_rto_prepare - 196 +196 tcp_process_refused_data - 196 +196 send_data - 196 +196 lwip_wget - 192 +192 ethernet_output - 192 +192 ping_recv - 188 +188 pbuf_memcmp - 184 +184 pbuf_copy_partial - 184 +184 httpc_free_state - 180 +180 tcp_send_fin - 172 +172 httpc_recv - 168 +168 tcp_output_control_segment_netif - 164 +164 send_error.isra - 164 +164 do_ops - 164 +164 raw_sendto - 160 +160 pbuf_realloc - 160 +160 pbuf_free - 160 +160 do_lwip_wget - 160 +160 do_lwip_tftp - 160 +160 tftp_init_common - 156 +156 tcp_rst_netif - 152 +152 udp_sendto - 144 +144 tftp_tmr - 144 +144 tcp_rst - 144 +144 uboot_lwip_if_init - 140 +140 tcp_pcb_remove - 140 +140 tcp_pbuf_prealloc - 140 +140 sys_timeout_abs - 140 +140 lwip_tftp - 140 +140 netif_do_set_ipaddr.isra - 136 +136 ip4_route - 136 +136 tcp_netif_ip_addr_changed - 132 +132 resend_data.isra - 132 +132 inet_chksum_pbuf - 132 +132 tcp_output_control_segment - 128 +128 pbuf_memfind - 128 +128 lwip_standard_chksum - 128 +128 tcp_rexmit_fast - 124 +124 tcp_new_port - 124 +124 tcp_close_shutdown_fin - 124 +124 pbuf_add_header_impl - 124 +124 tcp_send_empty_ack - 120 +120 httpc_create_request_string.constprop.isra - 120 +120 tftp_get - 116 +116 tcp_recved - 116 +116 tcp_pcb_purge - 116 +116 tftp_write - 112 +112 pbuf_free_header - 112 +112 httpc_tcp_connected - 112 +112 tftp_error - 108 +108 send_ack.isra - 108 +108 low_level_input.constprop - 108 +108 tcp_input_delayed_close - 104 +104 close_handle - 100 +100 sys_untimeout - 96 +96 memp_pools - 96 +96 tcp_keepalive - 92 +92 ip4_addr_isbroadcast_u32 - 92 +92 init_packet - 92 +92 tcp_kill_state - 88 +88 raw_new - 88 +88 ping_raw_init - 88 +88 lwip_ping_init - 88 +88 udp_sendto_if - 84 +84 tcp_update_rcv_ann_wnd - 84 +84 tcp_recv_null - 84 +84 pbuf_remove_header - 84 +84 pbuf_alloc_reference - 84 +84 udp_remove - 80 +80 tcp_get_next_optbyte - 80 +80 pbuf_alloced_custom - 80 +80 ip4_input_accept - 80 +80 httpc_close - 80 +80 etharp_free_entry - 80 +80 uboot_lwip_poll - 76 +76 tcpip_tcp_timer - 76 +76 udp_netif_ip_addr_changed - 72 +72 uboot_netif - 72 +72 tcp_output_alloc_header.constprop - 72 +72 raw_netif_ip_addr_changed - 72 +72 tcpip_try_callback - 68 +68 tcp_timer_needed - 68 +68 tcp_seg_copy - 68 +68 tcp_netif_ip_addr_changed_pcblist - 68 +68 ping_timeout - 68 +68 ethernetif_input - 68 +68 udp_new - 64 +64 pbuf_try_get_at - 64 +64 sys_timeout - 60 +60 pbuf_clone - 60 +60 tcp_seg_free - 56 +56 pbuf_cat - 56 +56 netif_get_by_index - 56 +56 low_level_output - 56 +56 _u_boot_list_2_cmd_2_lwipinfo - 56 +56 _u_boot_list_2_cmd_2_lwip - 56 +56 tftp_state 4 56 +52 tcp_tmr - 52 +52 tcp_rexmit_rto - 52 +52 tcp_segs_free - 48 +48 tcp_eff_send_mss_netif - 48 +48 pbuf_skip_const - 48 +48 ipfrag_free_pbuf_custom - 48 +48 httpc_tcp_poll - 48 +48 tcp_free_ooseq - 44 +44 tcp_close - 44 +44 pbuf_free_ooseq_callback - 44 +44 netif_issue_reports - 44 +44 ip_reass_dequeue_datagram - 44 +44 httpc_get_internal_addr - 44 +44 tftp_read - 40 +40 tftp - 40 +40 ip_data - 40 +40 etharp_request - 40 +40 do_lwip_info - 40 +40 ulwip_timeout_handler - 36 +36 raw_bind - 36 +36 memp_malloc - 36 +36 ip4_output_if - 36 +36 tcp_pcb_lists - 32 +32 pbuf_header_force - 32 +32 pbuf_clen - 32 +32 netif_set_up - 32 +32 netif_set_link_up - 32 +32 inseg - 32 +32 inet_chksum - 32 +32 tcp_next_iss - 28 +28 pbuf_get_at - 28 +28 httpc_tcp_err - 28 +28 do_lwip_init - 28 +28 tcp_rexmit_rto_commit - 24 +24 sys_now - 24 +24 settings - 24 +24 pbuf_copy - 24 +24 pbuf_chain - 24 +24 memp_free - 24 +24 __func__ 1243 1266 +23 ulwip_exit - 20 +20 tcp_trigger_input_pcb_close - 20 +20 tcp_poll - 20 +20 ping_send_now - 20 +20 pbuf_ref - 20 +20 str - 16 +16 ip4addr_ntoa - 16 +16 daddr - 16 +16 tcp_backoff - 13 +13 ulwip_loop_set - 12 +12 ulwip_in_loop - 12 +12 ulwip_enabled - 12 +12 ulwip_app_get_err - 12 +12 udp_recv - 12 +12 tftp_init_client - 12 +12 tcp_sent - 12 +12 tcp_recv - 12 +12 tcp_free - 12 +12 tcp_err - 12 +12 tcp_arg - 12 +12 net_process_received_packet 800 812 +12 icmp_time_exceeded - 12 +12 icmp_dest_unreach - 12 +12 udp_pcbs - 8 +8 tftp_open - 8 +8 tftp_close - 8 +8 tcphdr_opt2 - 8 +8 tcphdr - 8 +8 tcp_tw_pcbs - 8 +8 tcp_new - 8 +8 tcp_listen_pcbs - 8 +8 tcp_input_pcb - 8 +8 tcp_bound_pcbs - 8 +8 tcp_active_pcbs - 8 +8 tcp_abort - 8 +8 recv_data - 8 +8 reassdatagrams - 8 +8 raw_recv - 8 +8 raw_pcbs - 8 +8 ping_target - 8 +8 ping_pcb - 8 +8 pbuf_add_header - 8 +8 next_timeout - 8 +8 netif_null_output_ip4 - 8 +8 netif_list - 8 +8 netif_default - 8 +8 lwip_htons - 8 +8 lwip_htonl - 8 +8 httpc_tcp_sent - 8 +8 tcp_persist_backoff - 7 +7 ethzero - 6 +6 ethbroadcast - 6 +6 ulwip_app_err - 4 +4 udp_new_ip_type - 4 +4 uboot_net_use_lwip - 4 +4 tcpip_tcp_timer_active - 4 +4 tcp_ticks - 4 +4 seqno - 4 +4 mem_trim - 4 +4 mem_malloc - 4 +4 mem_free - 4 +4 loop_lwip - 4 +4 iss - 4 +4 ip_target - 4 +4 ip_chksum_pseudo - 4 +4 ip_addr_any - 4 +4 httpc_init_connection - 4 +4 ackno - 4 +4 udp_port - 2 +2 tcplen - 2 +2 tcphdr_optlen - 2 +2 tcphdr_opt1len - 2 +2 tcp_port - 2 +2 tcp_optidx - 2 +2 recv_acked - 2 +2 ping_seq_num - 2 +2 memp_UDP_PCB - 2 +2 memp_TCP_SEG - 2 +2 memp_TCP_PCB_LISTEN - 2 +2 memp_TCP_PCB - 2 +2 memp_TCPIP_MSG_INPKT - 2 +2 memp_TCPIP_MSG_API - 2 +2 memp_SYS_TIMEOUT - 2 +2 memp_REASSDATA - 2 +2 memp_RAW_PCB - 2 +2 memp_PBUF_POOL - 2 +2 memp_PBUF - 2 +2 memp_FRAG_PBUF - 2 +2 ip_reass_pbufcount - 2 +2 ip_id - 2 +2 tcp_timer_ctr - 1 +1 tcp_timer - 1 +1 tcp_active_pcbs_changed - 1 +1 recv_flags - 1 +1 pbuf_free_ooseq_pending - 1 +1 netif_num - 1 +1 flags - 1 +1 etharp_cached_entry - 1 +1 supported_nfs_versions 1 - -1 retry_action 1 - -1 net_boot_file_name_explicit 1 - -1 dhcp_option_overload 1 - -1 tftp_windowsize 2 - -2 tftp_window_size_option 2 - -2 tftp_next_ack 2 - -2 tftp_last_nack 2 - -2 tftp_block_size_option 2 - -2 tftp_block_size 2 - -2 ping_seq_number 2 - -2 last_op 2 - -2 env_flags_vartype_rep 7 5 -2 linefeed 3 - -3 wget_timeout_count 4 - -4 wget_loop_state 4 - -4 web_server_ip 4 - -4 timeout_count_max 4 - -4 timeout_count 4 - -4 tftp_timeout_count_max 4 - -4 tftp_remote_port 4 - -4 tftp_remote_ip 4 - -4 tftp_our_port 4 - -4 saved_tftp_block_size_option 4 - -4 retry_tcp_seq_num 4 - -4 retry_tcp_ack_num 4 - -4 retry_len 4 - -4 pkt_q_idx 4 - -4 packets 4 - -4 our_port 4 - -4 nfs_timeout_count 4 - -4 nfs_state 4 - -4 nfs_server_port 4 - -4 nfs_server_mount_port 4 - -4 nfs_server_ip 4 - -4 nfs_our_port 4 - -4 nfs_offset 4 - -4 nfs_len 4 - -4 nfs_download_state 4 - -4 net_ping_ip 4 - -4 net_dns_server 4 - -4 net_boot_file_expected_size_in_blocks 4 - -4 last_reg_lo 4 - -4 last_reg_hi 4 - -4 last_mask 4 - -4 last_data 4 - -4 last_addr_lo 4 - -4 last_addr_hi 4 - -4 initial_data_seq_num 4 - -4 http_ok 4 - -4 fs_mounted 4 - -4 filefh3_length 4 - -4 eth_common_init 4 - -4 dummy_handler 8 4 -4 dhcp_state 4 - -4 dhcp_server_ip 4 - -4 dhcp_leasetime 4 - -4 current_wget_state 4 - -4 bootp_try 4 - -4 bootp_num_ids 4 - -4 http_eom 5 - -5 bootfile1 5 - -5 timeout_ms 8 - -8 time_taken_max 8 - -8 time_start 16 8 -8 tftp_prev_block 8 - -8 tftp_load_size 8 - -8 tftp_load_addr 8 - -8 tftp_cur_block 8 - -8 tftp_block_wrap_offset 8 - -8 tftp_block_wrap 8 - -8 rpc_id 8 - -8 nfs_path 8 - -8 nfs_filename 8 - -8 miiphy_is_1000base_x 8 - -8 init_sequence_r 264 256 -8 image_url 8 - -8 distro_pxe_check 8 - -8 current_mii 8 - -8 content_length 8 - -8 bootp_timeout 8 - -8 bootp_start 8 - -8 tcp_get_tcp_state 12 - -12 do_wget 12 - -12 do_tftpb 12 - -12 do_nfs 12 - -12 do_dhcp 12 - -12 do_bootp 12 - -12 default_filename 13 - -13 bootfile3 14 - -14 content_len 15 - -15 reg_2_desc_tbl 16 - -16 pkt_q 16 - -16 mii_devs 16 - -16 bootp_ids 16 - -16 miiphy_get_current_dev 20 - -20 tcp_set_tcp_handler 24 - -24 pxe_default_paths 24 - -24 net_set_udp_handler 24 - -24 net_check_prereq 256 232 -24 miiphy_init 28 - -28 ping_timeout_handler 32 - -32 net_nis_domain 32 - -32 net_hostname 32 - -32 distro_bootmeth_pxe_ids 32 - -32 dirfh 32 - -32 initr_net 36 - -36 distro_bootmeth_pxe_bind 36 - -36 ip_to_string 40 - -40 distro_bootmeth_pxe_ops 40 - -40 net_send_udp_packet 44 - -44 label_boot 1944 1900 -44 env_flags_validate 632 588 -44 reg_3_desc_tbl 48 - -48 do_get_tftp 56 - -56 cmd_net 56 - -56 _u_boot_list_2_cmd_2_wget 56 - -56 _u_boot_list_2_cmd_2_tftpboot 56 - -56 _u_boot_list_2_cmd_2_pxe 56 - -56 _u_boot_list_2_cmd_2_ping 56 - -56 _u_boot_list_2_cmd_2_nfs 56 - -56 _u_boot_list_2_cmd_2_net 56 - -56 _u_boot_list_2_cmd_2_mii 56 - -56 _u_boot_list_2_cmd_2_dhcp 56 - -56 _u_boot_list_2_cmd_2_bootp 56 - -56 net_loop 652 592 -60 net_eth_hdr_size 60 - -60 bootp_reset 60 - -60 net_root_path 64 - -64 filefh 64 - -64 do_bootvx 816 748 -68 miiphy_set_current_dev 72 - -72 basename 72 - -72 pxe_get_file_size 76 - -76 copy_filename 76 - -76 distro_pxe_getfile 80 - -80 tftp_init_load_addr 92 - -92 miiphy_read 92 - -92 extract_range 92 - -92 miiphy_write 96 - -96 miiphy_get_active_dev 96 - -96 distro_pxe_read_file 96 - -96 wget_fail 104 - -104 skip_num 104 - -104 miiphy_get_dev_by_name 104 - -104 dump_field 104 - -104 do_bdinfo 432 328 -104 bootp_timeout_handler 104 - -104 nfs_timeout_handler 108 - -108 cmd_pxe_sub 112 - -112 nfs_umountall_req 120 - -120 _u_boot_list_2_driver_2_bootmeth_pxe 120 - -120 do_ping 124 - -124 tftp_filename 128 - -128 reg_9_desc_tbl 128 - -128 reg_10_desc_tbl 128 - -128 distro_pxe_boot 128 - -128 tftp_timeout_handler 132 - -132 do_pxe 132 - -132 nfs_umountall_reply 136 - -136 lmb_get_free_size 136 - -136 format_mac_pxe 136 - -136 miiphy_listdev 144 - -144 efi_net_set_dhcp_ack 144 - -144 wget_timeout_handler 148 - -148 nfs_mount_reply 148 - -148 dhcp_packet_process_options 148 - -148 eth_validate_ethaddr_str 152 - -152 do_pxe_get 156 - -156 reg_0_desc_tbl 160 - -160 net_parse_bootfile 160 - -160 miiphy_info 160 - -160 get_pxelinux_path 160 - -160 do_net 164 - -164 net_auto_load 172 - -172 do_net_list 176 - -176 rpc_lookup_reply 180 - -180 nfs_readlink_req 184 - -184 nfs_mount_req 188 - -188 reg_5_desc_tbl 192 - -192 reg_4_desc_tbl 192 - -192 miiphy_speed 200 - -200 miiphy_duplex 200 - -200 nfs_read_req 224 - -224 do_pxe_boot 248 - -248 reg_1_desc_tbl 256 - -256 mii_reg_desc_tbl 256 - -256 nfs_send 260 - -260 wget_start 268 - -268 ping_start 276 - -276 nfs_lookup_reply 280 - -280 rpc_req 300 - -300 eth_initialize 300 - -300 distro_pxe_read_bootflow 300 - -300 nfs_readlink_reply 328 - -328 nfs_lookup_req 328 - -328 ping_receive 332 - -332 pxe_get 376 - -376 nfs_read_reply 396 - -396 wget_send_stored 444 - -444 nfs_start 468 - -468 dhcp_process_options 508 - -508 tftp_send 560 - -560 nfs_handler 580 - -580 bootp_request 612 - -612 dhcp_extended 616 - -616 netboot_common 632 - -632 default_environment 4444 3800 -644 tftp_start 912 - -912 dhcp_handler 1000 - -1000 wget_handler 1092 - -1092 tftp_handler 1304 - -1304 nfs_path_buff 2048 - -2048 do_mii 2124 - -2124 Total: Before=722283, After=738425, chg +2.23%
On Thu, 8 Jun 2023 at 02:07, Tom Rini trini@konsulko.com wrote:
On Wed, May 24, 2023 at 10:18:13PM +0200, Simon Goldschmidt wrote:
Hi Maxim, Tom,
On 24.05.2023 16:05, Maxim Uvarov wrote:
On Tue, 23 May 2023 at 03:23, Tom Rini trini@konsulko.com wrote:
On Mon, May 22, 2023 at 12:40:49PM -0400, Maxim Uvarov wrote:
On Mon, 22 May 2023 at 10:20, Tom Rini trini@konsulko.com wrote:
> On Mon, May 22, 2023 at 04:33:57PM +0300, Ilias Apalodimas wrote: > > Hi Maxim > > > > On Mon, 22 May 2023 at 12:01, Maxim Uvarov maxim.uvarov@linaro.org > wrote: > > > > > > My measurements for binary after LTO looks like: > > > > > > U-boot WGET | LWIP WGET + ping | LWIP WGET| diff bytes| diff % > > > 870728 | 915000 | 912560 | > 41832 | 4.8 > > > > > > I think you'll need to analyze that a bit more. First of all I don't > > think the '+ping' tab is useful. What is is trying to achieve? >
To show the difference of extra bytes if we add a ping app on top.
> > - How was LWIP compiled? >
It has a really huge configuration. I tried to turn off everything off everything what can impact on size but still make http app work: #define LWIP_HAVE_LOOPIF 0 #define LWIP_NETCONN 0 #define LWIP_SOCKET 0 #define SO_REUSE 0 #define LWIP_STATS 0 #define PPP_SUPPORT 0
Disabling loopback: #define LWIP_NETIF_LOOPBACK 0 can lower to 912288 bytes.
And it's the same compilation option (optimization for size) as the main u-boot. I will do more experiments, but I think the goal is not to turn
off
everything.
> > - Was ipv6 supported? >
No. I.e. when I sent results it was enabled on the compilation stage but not used. I just checked that size remains the same if IPv6 is not even compiled.
> > - Can we strip it down even further? > > >
There is always room for optimization. I think I tried to turn off everything that is configurable with defines. I can play with disable IP reassembly and things like that or figure out which functions have more size and if it's possible to exclude them.
> > In general please give as much information as you can with what we > > gain in functionality from LWIP with those extra bytes of code. > > The main idea is to reuse a maintainable IP stack outside of U-boot.
LWIP
can give a nice separation between IP stack code and network application code. I.e. application should not take care about any TCP details (SYN, ACK, retransmission, reassembly etc) and should open connection and use functions similar to recv() and send() to transfer data. Data means application data, no network packets. And LWIP allows us to do that. Because LWIP has an API similar to sockets, it has to be very easy to
port
a linux application to LWIP. Then you can test it with a tap device. Then copy sources to U-boot, add a small integration layer (cmd command to call), compile and use.
So my suggestion was:
- do not maintain new network stack code in the current U-boot. Use lwip
sources as an external project. All bugs related to network stack go to lwip project first, then sync with U-boot.
- maintain network apps code* or -- inside U-boot. Write our own code for application and maintain it
inside U-boot. -- inside LWIP. Add examples to LWIP which are suitable for both
U-boot
and LWIP.
- Let's define a U-boot network application as a cmd command. It might be
ping, wget (http or https download), telnet, arp dns etc..
Let's consider the real use case, like HTTPS download client. We need to enable TLS connection, validate certificates, then do http download. Looking at the current code of wget command it's quite difficult to implement this due to the application having some protol level things. On the other side we can find embedTLS examples to do https download on sockets. If LWIP socket API is ported then the only thing you need to do
is
change socket() -> lwip_socket(), recv()->lwip_recv(),
send()->lwip_send()
and etc, even function names are similar. If LWIP socket API is not supported, then use callback API for recv() and send(), which are also easy.
So yes we add extra bytes, but that will allow us to write more complex apps, use standard debug tools, use applications with very minimal integration changes, use help from the LWIP community to fix protocol
bugs,
etc.. Bunch of things already implemented there:
- ipv6
- dhcp
- snmp
- igmp
- dns
- tcp and udp and raw.
- loopback
- netconn
- socket
- stats
- ppp
(I just followed configurable defines).
And please make sure to disable the previous support, my guess fro that > much growth is that you didn't. >
# CONFIG_PROT_TCP is not set # CONFIG_PROT_UDP is not set # CONFIG_UDP_CHECKSUM is not set # CONFIG_UDP_FUNCTION_FASTBOOT is not set # CONFIG_CMD_WGET is not set
I think you need to step back and figure out a better way to measure the size change and growth.
I am not interested in a path that long term means two networking stacks in U-Boot.
I am not interested in massively growing the overall binary size for every platform. Given how much larger just TCP support is, that's strongly implying a huge growth for the older use cases too.
But I also suspect given the overall reputation that LWIP enjoys, there's something amiss here.
-- Tom
+cc lwip-devel@ mailing list, maybe they have something to add.
I do think using lwIP instead of "inventing yet another IP stack" is a good idea! However, in terms of code size, lwIP will lose against what's in U-Boot at present. And this is only natural, as lwIP is a "full-size" stack supporting multiple concurrently running applications while the current IP stack in U-Boot is rather "crippled" down to just what the implementor needed at the time of writing.
One example of this is that (if I remember correctly), U-Boot only has one single network packet buffer, while lwIP has support for multiple buffers. When speaking of TCP (forgive me if I'm wrong, I've lost track of that development in U-Boot about 3 years ago), we're comparing "we have implemented everything we need so that it just kind of works" to "we can easily add a HTTPS client to download something over the internet just by enabling more compile options".
Also, when comparing lwIP to U-Boot TCP code size, keep in mind that U-Boot TCP (at least that of some years ago) is far from complete when compared to lwIP!
lwIP is meant to be highly configurable and we're always open to add yet more options to leave out more code when it's not needed. However, I think there are some design decisions that will make lwIP larger than the current IP stack in U-Boot. To me, that's a natural result of having a "generic code" approach vs "developed to our needs". However, while DHCP + BOOTP and even a simple network console was rather easy to implement, I would not recommend implementing your own HTTPS download but rather using the existing lwIP + apps for that.
In the end, I cannot take the decision from you. In my opinion, lwIP would be the better decision in terms of future work load and compatibility, but in the short run, it *will* lead to bigger binaries at least in some setups. And I do know from my past that it sometimes has been a pain to try and stuff a new U-Boot release into the existing space of flash or RAM, so that's not an easy decision.
If you do take the lwIP approach however, let us know if we can help!
Given Maxim's more recent experiments, I'm sure we can come up with something that works overall. There's hopefully a place or two U-Boot people can help introduce a tunable or two to lwIP to bring some sizes down. But I think it's overall looking to be the right direction.
-- Tom