Re: [PATCH] net: lwip: support syslog

On Tue, 25 Aug 2026 at 19:59, James Hilliard <[email protected]> wrote:
>
> LOG_SYSLOG depends on NET, but the raw Ethernet and UDP header
> builders it uses are only available with the legacy network stack. This
> makes LOG_SYSLOG fail to build with NET_LWIP.
>
> Provide lwIP implementations using the selected Ethernet device and its
> indexed IP address from the environment. Move the shared declarations to
> net-common.h and extend the syslog test to check the source MAC address
> and IPv4 header checksum.
>
> Signed-off-by: James Hilliard <[email protected]>
> ---
>  include/net-common.h   |  7 ++++++
>  include/net-legacy.h   |  4 ----
>  net/lwip/net-lwip.c    | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  test/log/syslog_test.c |  2 ++
>  test/log/syslog_test.h |  4 ++--
>  5 files changed, 69 insertions(+), 6 deletions(-)
>
> diff --git a/include/net-common.h b/include/net-common.h
> index 0c260873c2c..3084a2b2a57 100644
> --- a/include/net-common.h
> +++ b/include/net-common.h
> @@ -362,6 +362,13 @@ struct ethernet_hdr {
>  /* Ethernet header size */
>  #define ETHER_HDR_SIZE (sizeof(struct ethernet_hdr))
>
> +/* Set Ethernet header; returns the size of the header */
> +int net_set_ether(uchar *xet, const uchar *dest_ethaddr, uint prot);
> +
> +/* Set IPv4 and UDP headers */
> +void net_set_udp_header(uchar *pkt, struct in_addr dest, int dport,
> +                       int sport, int len);
> +
>  /**
>   * net_random_ethaddr - Generate software assigned random Ethernet address
>   * @addr: Pointer to a six-byte array containing the Ethernet address
> diff --git a/include/net-legacy.h b/include/net-legacy.h
> index d3b122c9062..d7f55d34a30 100644
> --- a/include/net-legacy.h
> +++ b/include/net-legacy.h
> @@ -344,15 +344,11 @@ int net_loop(enum proto_t);
>  /* Get size of the ethernet header when we send */
>  int net_eth_hdr_size(void);
>
> -/* Set ethernet header; returns the size of the header */
> -int net_set_ether(uchar *xet, const uchar *dest_ethaddr, uint prot);
>  int net_update_ether(struct ethernet_hdr *et, uchar *addr, uint prot);
>
>  /* Set IP header */
>  void net_set_ip_header(uchar *pkt, struct in_addr dest, struct in_addr source,
>                        u16 pkt_len, u8 proto);
> -void net_set_udp_header(uchar *pkt, struct in_addr dest, int dport,
> -                       int sport, int len);
>
>  /* Callbacks */
>  rxhand_f *net_get_udp_handler(void);   /* Get UDP RX packet handler */
> diff --git a/net/lwip/net-lwip.c b/net/lwip/net-lwip.c
> index 8f8f9d69020..4dd8f0d2ce7 100644
> --- a/net/lwip/net-lwip.c
> +++ b/net/lwip/net-lwip.c
> @@ -159,6 +159,64 @@ static int get_udev_ipv4_info(struct udevice *dev, ip4_addr_t *ip,
>         return 0;
>  }

If these are specific to LOG_SYSLOG functionality I think they should
be guarded by LOG_SYSLOG

> +int net_set_ether(uchar *xet, const uchar *dest_ethaddr, uint prot)
> +{
> +       struct ethernet_hdr *et = (struct ethernet_hdr *)xet;
> +       const uchar *src = eth_get_ethaddr();
> +
> +       memcpy(et->et_dest, dest_ethaddr, ARP_HLEN);
> +       if (src)
> +               memcpy(et->et_src, src, ARP_HLEN);
> +       else
> +               memset(et->et_src, 0, ARP_HLEN);
> +       et->et_protlen = htons(prot);
> +
> +       return ETHER_HDR_SIZE;
> +}
> +
> +static void net_lwip_set_ip_header(uchar *pkt, struct in_addr dest,
> +                                  struct in_addr source, u16 pkt_len,
> +                                  u8 proto)
> +{
> +       static u16 ip_id;
> +       struct ip_udp_hdr *ip = (struct ip_udp_hdr *)pkt;
> +
> +       ip->ip_hl_v = 0x45;
> +       ip->ip_tos = 0;
> +       ip->ip_len = htons(pkt_len);
> +       ip->ip_p = proto;
> +       ip->ip_id = htons(ip_id++);
> +       ip->ip_off = htons(IP_FLAGS_DFRAG);
> +       ip->ip_ttl = 255;
> +       ip->ip_sum = 0;
> +       memcpy(&ip->ip_src, &source, sizeof(source));
> +       memcpy(&ip->ip_dst, &dest, sizeof(dest));
> +       ip->ip_sum = compute_ip_checksum(ip, IP_HDR_SIZE);
> +}
> +
> +void net_set_udp_header(uchar *pkt, struct in_addr dest, int dport, int sport,
> +                       int len)
> +{
> +       struct ip_udp_hdr *ip = (struct ip_udp_hdr *)pkt;
> +       struct in_addr source = {};
> +       ip4_addr_t addr, mask, gateway;
> +       struct udevice *dev = eth_get_dev();
> +       u16 pkt_len = IP_UDP_HDR_SIZE + len;
> +
> +       if (len & 1)
> +               pkt[IP_UDP_HDR_SIZE + len] = 0;
> +
> +       if (dev && !get_udev_ipv4_info(dev, &addr, &mask, &gateway))
> +               source.s_addr = addr.addr;
> +
> +       net_lwip_set_ip_header(pkt, dest, source, pkt_len, IPPROTO_UDP);
> +
> +       ip->udp_src = htons(sport);
> +       ip->udp_dst = htons(dport);
> +       ip->udp_len = htons(UDP_HDR_SIZE + len);
> +       ip->udp_xsum = 0;
> +}
> +
>  /*
>   * Initialize DNS via env
>   */
> diff --git a/test/log/syslog_test.c b/test/log/syslog_test.c
> index b6c0631aaf6..f848506fb1c 100644
> --- a/test/log/syslog_test.c
> +++ b/test/log/syslog_test.c
> @@ -34,11 +34,13 @@ int sb_log_tx_handler(struct udevice *dev, void *packet, unsigned int len)
>
>         /* Check Ethernet header */
>         ut_asserteq_mem(&eth_hdr->et_dest, net_bcast_ethaddr, ARP_HLEN);
> +       ut_asserteq_mem(&eth_hdr->et_src, eth_get_ethaddr(), ARP_HLEN);
>         ut_asserteq(ntohs(eth_hdr->et_protlen), PROT_IP);
>
>         /* Check IP header */
>         buf += sizeof(struct ethernet_hdr);
>         ip_udp_hdr = (struct ip_udp_hdr *)buf;
> +       ut_assert(ip_checksum_ok(ip_udp_hdr, IP_HDR_SIZE));
>         ut_asserteq(ip_udp_hdr->ip_p, IPPROTO_UDP);
>         ut_asserteq(ip_udp_hdr->ip_dst.s_addr, 0xffffffff);
>         ut_asserteq(ntohs(ip_udp_hdr->udp_dst), 514);
> diff --git a/test/log/syslog_test.h b/test/log/syslog_test.h
> index 39cce4ed498..89c86541f5e 100644
> --- a/test/log/syslog_test.h
> +++ b/test/log/syslog_test.h
> @@ -31,8 +31,8 @@ struct sb_log_env {
>   *
>   * The following checks are executed:
>   *
> - * * the Ethernet packet indicates a IP broadcast message
> - * * the IP header is for a local UDP broadcast message to port 514
> + * * the Ethernet packet uses the selected interface and broadcast destination
> + * * the IP header checksum is valid and describes a UDP broadcast to port 514
>   * * the UDP payload matches the expected string
>   *
>   * After testing the pointer to the expected string is set to NULL to signal
>
> ---
> base-commit: 964ad5b5c91b7be56e443e899d7f873e6aa8c9fc
> change-id: 20260825-lwip-syslog-v1-a5625eba2ea3
>
> Best regards,
> --
> James Hilliard <[email protected]>
>