[U-Boot] [U-boot] Question about bootp structure pack

[Eric BOUXIROT]

Hi everyone,



I’m using u-boot-2015.07 in one of my project based on vpac270 soc module.

u-boot is well configured and build is fine without error.

Gcc is v3.4.5 and glibc v2.3.6 built by crosstool 0.43 for
arm-softfloat-linux-gnu



My problem is when i use DHCP command to retrieve a file from my TFTP
server, i can’t get any IP from the DHCP server.

After analysing ethernet frames on server side i found that frame do not
arrive at all on server.

After checking debug détails on U-boot, it seem bootp frame is not good
because of some 0x00 paddings Inside the frame. (at end of header for
example)



If i add the attribute packed to the bootp header struct and ethernet
header, now all is working fine !



In net/bootp.h :

struct bootp_hdr {

                u8                           bp_op;                 /*
Operation                                     */

# define OP_BOOTREQUEST       1

# define OP_BOOTREPLY             2

                u8                           bp_htype;          /* Hardware
type                           */

# define HWT_ETHER     1

                u8                           bp_hlen;             /*
Hardware address length       */

# define HWL_ETHER     6

                u8                           bp_hops;            /* Hop
count (gateway thing)    */

                u32                        bp_id;                  /*
Transaction ID                             */

                u16                        bp_secs;             /* Seconds
since boot                   */

                u16                        bp_spare1;        /*
Alignment                                     */

                struct in_addr   bp_ciaddr;          /* Client IP
address                        */

                struct in_addr   bp_yiaddr;         /* Your (client) IP
address           */

                struct in_addr   bp_siaddr;          /* Server IP
address                       */

                struct in_addr   bp_giaddr;         /* Gateway IP
address                  */

                u8                           bp_chaddr[16]; /* Client
hardware address         */

                char                       bp_sname[64]; /* Server host
name                      */

                char                       bp_file[128];     /* Boot file
name                            */

                char                       bp_vend[OPT_FIELD_SIZE]; /*
Vendor information         */

} __attribute__((packed));



#define BOOTP_HDR_SIZE          sizeof(struct bootp_hdr)



And in include/net.h

struct ethernet_hdr {

                u8                           et_dest[6];        /*
Destination node                       */

                u8                           et_src[6];            /*
Source node                                */

                u16                        et_protlen;        /* Protocol
or length                     */

} __attribute__((packed));



I think the uboot src should work as is, because I have checked uboot
source modification since 2015.07, but no changes on the struct definition
and header_size still made with sizeof(struct).

So i think, the problem come from my side and perhaps from gcc itself.



But i don’t understand why gcc should pack these structs.. i think normal
use is to not pack.. except if makefile include some build option to do
that, my gcc toolchain do not understand..



Someone can help me to understand what i made wrong ? and help me to
resolve this problem without patching  ?