I have an HTTPD implementation, derived from the raw one in contrib/, that showed a strange behavior receiving fragmented packets. Note: In the attached Wireshark capture there's a fragment of communication that exhibits such problem. In the capture file .130 is the host/web-client, and .199 is the the lwIP 1.3.1 server.
I'm receiving an HTTP POST message from a browser (in this case Google Chrome, but I have reports that could have happened with different ones), from a login page with a form that sends "username" and "password" fields. While I've always found browsers to fill a single packet with all the application headers, and the username/password payload, in this case the request is split in two parts: the first one with just headers, the second with payload. My modified httpd.c code recomposes the pbuf chain received in a single buffer, as the tcp_recv() handler is called, and that works in all other cases, but this one. In capture file: the POST request is composed of packet 4 and 6, but in between there's a packet 5, coming from server: the lwIP server believes that packet 4 has no followers, sees no username/password payload, and instructs the browser to reload the login page. Maybe I'm just unaware of what all this means, but... why (having IP_REASSEMBLY defined to 1) the two packets aren't recomposed in a pbuf chain? lwIP (1.3.1) is configured with ---------------------------------------------------------------------- #define NO_SYS 1 #define SYS_LIGHTWEIGHT_PROT 1 #define MEM_ALIGNMENT 4 #define MEM_SIZE (128 * 1024) #define MEMP_NUM_RAW_PCB 16 // 8 #define MEMP_NUM_UDP_PCB 8 // 4 #define MEMP_NUM_PBUF 32 // default 16 #define MEMP_NUM_TCP_PCB 128 // 32 // default 5 #define MEMP_NUM_TCP_PCB_LISTEN 8 #define MEMP_NUM_TCP_SEG 256 // default 16 #define PBUF_POOL_SIZE 128 // default 16 #define LWIP_DHCP 1 // default 0 #define DHCP_DOES_ARP_CHECK 1 #define LWIP_AUTOIP 1 #define LWIP_DHCP_AUTOIP_COOP 1 #define TCP_WND 4096 // default 2048 #define TCP_MSS 1460 #define TCP_SND_BUF (8 * TCP_MSS) #define PBUF_LINK_HLEN 16 // default 14 #define LWIP_NETCONN 0 // default 1 #define LWIP_SOCKET 0 // default 1 #define LWIP_COMPAT_SOCKETS 0 #define LWIP_NETIF_HOSTNAME 1 #define LWIP_DNS 1 ---------------------------------------------------------------------- Lou ____________________________________________________________ Receive Notifications of Incoming Messages Easily monitor multiple email accounts & access them with a click. Visit http://www.inbox.com/notifier and check it out!
split.pcap
Description: Binary data
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