On Wed, Mar 24, 2010 at 9:24 AM, David Baird <dhba...@gmail.com> wrote:
> On Wed, Mar 24, 2010 at 9:05 AM, Martin Sigwald <msigw...@gmail.com> wrote:
>> While I could gather, both the open system called generated by the DB and
>> the socket() syscall are returning a FD=3.
>> That is, they are both trying to use the same filedescriptor. My guess is
>> packets get sent to that file descriptor, instead of the port. How can I
>> changed this? I just followed standar procedure to allocate a socket:
>> sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP))
>>
>> Shouldn't the Kernel take care of this and provide an unused FD??
>
> According to the strace, the kernel is taking care of that properly.
> You get a socket, call sendto, select, recvfrom, then close it. And
> then you open guido.db. Since you just closed your socket, the fd=3
> is reused for guido.db. This is perfectly legitimate. Something else
> funny is going on. Here's the relevant portions from the strace:
Actually, I just realized that a socket is opened twice in your
strace. So, here's the portion that includes both socket opens and
the database open:
First socket open and close:
socket(PF_INET, SOCK_RAW, IPPROTO_ICMP) = 3
setsockopt(3, SOL_IP, IP_HDRINCL, [1], 4) = 0
sendto(3, "E\0\34\0Eg\0\0\377\1P\223\0\0\0\0\n\0\0\3\10\0;\320#\306"...,
28, 0, {sa_family=AF_INET, sin_port=htons(0),
sin_addr=inet_addr("10.0.0.3")}, 16) = 28
select(4, [3], NULL, NULL, {2, 500000}) = 1 (in [3], left {2, 496000})
recvfrom(3, "e\0\0\0...@\0\0@\0015\233\n\0\0\3\n\0\0\4\0\0C\320#\306"...,
28, 0, {sa_family=AF_INET, sin_port=htons(0),
sin_addr=inet_addr("10.0.0.3")}, [16]) = 28
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 2), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0xb7f16000
write(1, "El Server 10.0.0.3 esta en el es"..., 43) = 43
close(3) = 0
Database open and close (with a dup in the middle that also creates fd=4)...
getcwd("/home/martin", 5000) = 13
open("/home/martin/guido.db", O_RDWR|O_CREAT|O_LARGEFILE, 0644) = 3
fcntl64(3, F_GETFD) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC) = 0
fstat64(3, {st_mode=S_IFREG|0777, st_size=2048, ...}) = 0
dup(3) = 4
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0xb7537000
mprotect(0xb7537000, 4096, PROT_NONE) = 0
clone(child_stack=0xb7d374c4,
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
parent_tidptr=0xb7d37bd8, {entry_number:6, base_addr:0xb7d37b90,
limit:1048575, seg_32bit:1, contents:0, read_exec_only:0,
limit_in_pages:1, seg_not_present:0, useable:1},
child_tidptr=0xb7d37bd8) = 6240
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0xb6d36000
mprotect(0xb6d36000, 4096, PROT_NONE) = 0
clone(child_stack=0xb75364c4,
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
parent_tidptr=0xb7536bd8, {entry_number:6, base_addr:0xb7536b90,
limit:1048575, seg_32bit:1, contents:0, read_exec_only:0,
limit_in_pages:1, seg_not_present:0, useable:1},
child_tidptr=0xb7536bd8) = 6241
close(4) = 0
_llseek(3, 0, [0], SEEK_SET) = 0
read(3, "SQLite format 3\0\4\0\1\1\0@ \0\0\0\4\0\0\0\0"..., 100) = 100
close(3) = 0
getuid32() = 0
And second socket open and close....
socket(PF_INET, SOCK_RAW, IPPROTO_ICMP) = 3
setsockopt(3, SOL_IP, IP_HDRINCL, [1], 4) = 0
sendto(3, "E\0\34\0Hs\4\10\377\1I\177\0\0\0\0\n\0\0\3\10\0\276\256"...,
28, 0, {sa_family=AF_INET, sin_port=htons(0),
sin_addr=inet_addr("10.0.0.3")}, 16) = 28
select(4, [3], NULL, NULL, {2, 500000}) = 0 (Timeout)
write(1, "TIMEOUT\n", 8) = 8
close(3) = 0
In both cases that you call sendto, it appears to have succeeded (i.e.
because they returned a positive value, i.e. 28). In the second case,
select timed out (as you said it does).
I don't notice any cases of where a stale file descriptor is being
accessed. I'm stumped :-/
-David
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