On 8 nov 2011 21:05 "goldsi...@gmx.de" <goldsi...@gmx.de> wrote:
> <w...@brolinembedded.se> wrote: > > Yes, it is. It is a mandatory feature for certain protocols, such as > > the industrial control protocol "EtherNet/IP" > > <http://en.wikipedia.org/wiki/Ethernet/IP> > > That's interesting. Since I know of at least one Ethernet/IP stack > being > ported to linux, do you know whether/how linux allows changing the > VLAN > header per socket? > > > The problem with adding VLAN PCP to LwIP is that a socket level > > variable must somehow be communicated down to the link layer for > > each > > frame. There does not seem to be a easy way of doing this. > Thinkig about it, we already have a mechanism for that: the per-pcb > ARP > entry cache. In the same manner as this, we could add members to > struct > netif which configure VLAN settings and change them before calling one > of the ip_output functions (although that set/reset code would be > scattered around tcp, udp, raw, icmp and igmp). > > Simon > I have rewritten our VLAN PCP implementation, taking advantage of the ARP entry cache feature. In short, these are the modifications I have done. This snippet of code occurs in several places in LwIP: ************ #if LWIP_NETIF_HWADDRHINT netif->addr_hint = &(pcb->addr_hint); #endif /* LWIP_NETIF_HWADDRHINT*/ err = ip_output_if(q, src_ip, dst_ip, pcb->ttl, pcb->tos, IP_PROTO_UDPLITE, netif); #if LWIP_NETIF_HWADDRHINT netif->addr_hint = NULL; #endif /* LWIP_NETIF_HWADDRHINT*/ ************ In all places I have replaced it with macros like this: ************ LWIP_SET_HINTS( netif, pcb ); err = ip_output_if(q, src_ip, dst_ip, pcb->ttl, pcb->tos, IP_PROTO_UDPLITE, netif); LWIP_RESET_HINTS( netif ); ************ The macro copies both the ARP entry cache hint, as well as the VLAN PCP variable. I have changed the last argument of the function ip_output_hinted() from "u8_t *addr_hint" to "struct ip_pcb* pcb_hint". This allows other information besides the ARP entry cache to be copied from the pcb to the netif. The function tcp_rst did not support the ARP entry cache feature. I have added it by modifying tcp_rst like this: ************ tcp_rst(u32_t seqno, u32_t ackno, ip_addr_t *local_ip, ip_addr_t *remote_ip, u16_t local_port, u16_t remote_port #if LWIP_USE_HINTS , struct ip_pcb *pcb #endif /* LWIP_USE_HINTS */ ) ************ I have modified pbuf_alloc to allocate room for the VLAN tag, like this: ************ case PBUF_LINK: /* add room for link layer header */ offset += PBUF_LINK_HLEN; #if LWIP_VLAN_PCP /* add room for VLAN header */ offset += PBUF_VLAN_HLEN; #endif /* LWIP_VLAN_PCP */ break; ************ There is also new code in place in etharp_output to actually add the VLAN tag. What do you think about this solution? Regards, Timmy Brolin
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