[Bug libc/15015] New: getaddrinfo returns EAI_SERVICE with SOCK_RAW

["pablo at gnumonks dot org" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=15015

             Bug #: 15015
           Summary: getaddrinfo returns EAI_SERVICE with SOCK_RAW
           Product: glibc
           Version: 2.16
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: unassigned@sourceware.org
        ReportedBy: pablo@gnumonks.org
                CC: drepper.fsp@gmail.com
    Classification: Unclassified


Hi,

getaddrinfo returns EAI_SERVICE with SOCK_RAW. That's consistent with what you
can read at sysdeps/posix/getaddrinfo.c, line 125:

  { SOCK_RAW, 0, GAI_PROTO_PROTOANY|GAI_PROTO_NOSERVICE, true, "raw" }
                                    ^-----------------^

That function returns that error if the GAI_PROTO_NOSERVICE flag is set.

However, strace shows that, when getaddrinfo is called with SOCK_RAW, the
address information is retrieves from the kernel via netlink as this trace
below shows:

$ strace ./fr
[...]
socket(PF_NETLINK, SOCK_RAW, 0)         = 3
bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
getsockname(3, {sa_family=AF_NETLINK, pid=5936, groups=00000000}, [12]) = 0
sendto(3, "\24\0\0\0\26\0\1\3+\230\256P\0\0\0\0\0\0\0\0", 20, 0,
{sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
msg_iov(1)=[{"0\0\0\0\24\0\2\0+\230\256P0\27\0\0\2\10\200\376\1\0\0\0\10\0\1\0\177\0\0\1"...,
4096}], msg_controllen=0, msg_flags=0}, 0) = 108
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
msg_iov(1)=[{"@\0\0\0\24\0\2\0+\230\256P0\27\0\0\n\200\200\376\1\0\0\0\24\0\1\0\0\0\0\0"...,
4096}], msg_controllen=0, msg_flags=0}, 0) = 128
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
msg_iov(1)=[{"\24\0\0\0\3\0\2\0+\230\256P0\27\0\0\0\0\0\0\1\0\0\0\24\0\1\0\0\0\0\0"...,
4096}], msg_controllen=0, msg_flags=0}, 0) = 20

Let me decipher that netlink trace:

1) bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
                                                           ^^
   bind this socket to rtnetlink

2) Send the request message to ask for the address information.

sendto(3, "\24\0\0\0\26\0\1\3+\230\256P\0\0\0\0\0\0\0\0", 20, 0,
{sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20

3) This gets the multipart message with the information that we
requested:

recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
msg_iov(1)=[{"0\0\0\0\24\0\2\0+\230\256P0\27\0\0\2\10\200\376\1\0\0\0\10\0\1\0\177\0\0\1"...,
4096}], msg_controllen=0, msg_flags=0}, 0) = 108
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
msg_iov(1)=[{"@\0\0\0\24\0\2\0+\230\256P0\27\0\0\n\200\200\376\1\0\0\0\24\0\1\0\0\0\0\0"...,
4096}], msg_controllen=0, msg_flags=0}, 0) = 128
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},

But, even if the information is successfully retrieved, it is later on
discarded because of using SOCK_RAW.

Is there any reason for that behaviour? It seems inconsistent to me, ie.
retrieve address records from the kernel correctly but, later on, discard them
because that flag is set.

Thank you!

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