On Wed, Jun 26, 2013 at 01:27:19PM -0400, Vlad Yasevich wrote:
> On 06/26/2013 01:01 PM, Daniel Borkmann wrote:
> >In order to avoid making code that deals with printing both, IPv4 and
> >IPv6 addresses, unnecessary complicated as for example ...
> >
> > if (sa.sa_family == AF_INET6)
> > printk("... %pI6 ...", sin6_addr);
> > else
> > printk("... %pI4 ...", sin_addr.s_addr);
> >
> >... it would be better to introduce a format specifier that can deal
> >with those kind of situations internally; just as we have a "struct
> >sockaddr" for generic mapping into "struct sockaddr_in" or "struct
> >sockaddr_in6" as e.g. done in "union sctp_addr". Then, we could
> >reduce the above statement into something like:
> >
> > printk("... %pIg ..", &sockaddr);
> >
> >While we're at it, support for both %pig/%pIg, where 'g' stands for
> >generic, comes for free. In case our pointer is NULL, pointer() then
> >deals with that already at an earlier point in time internally.
> >
> >Likely, there are many other areas than just SCTP in the kernel to make
> >use of this extension as well.
> >
> >Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
> >---
> > lib/vsprintf.c | 18 ++++++++++++++++--
> > 1 file changed, 16 insertions(+), 2 deletions(-)
>
> I think you should also update Documentation/printk-formats.txt
>
> -vlad
>
Just FYI, Cong Wang just posted a patch series to netdev to make generic
printing of addresses possible
http://marc.info/?l=linux-netdev&m=137231556918786&w=2
Neil
> >
> >diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> >index e149c64..7243742 100644
> >--- a/lib/vsprintf.c
> >+++ b/lib/vsprintf.c
> >@@ -1004,10 +1004,10 @@ int kptr_restrict __read_mostly;
> > * - 'MF' For a 6-byte MAC FDDI address, it prints the address
> > * with a dash-separated hex notation
> > * - '[mM]R' For a 6-byte MAC address, Reverse order (Bluetooth)
> >- * - 'I' [46] for IPv4/IPv6 addresses printed in the usual way
> >+ * - 'I' [46g] for IPv4/IPv6 addresses printed in the usual way
> > * IPv4 uses dot-separated decimal without leading 0's (1.2.3.4)
> > * IPv6 uses colon separated network-order 16 bit hex with leading 0's
> >- * - 'i' [46] for 'raw' IPv4/IPv6 addresses
> >+ * - 'i' [46g] for 'raw' IPv4/IPv6 addresses
> > * IPv6 omits the colons (01020304...0f)
> > * IPv4 uses dot-separated decimal with leading 0's (010.123.045.006)
> > * - '[Ii]4[hnbl]' IPv4 addresses in host, network, big or little endian order
> >@@ -1093,6 +1093,18 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
> > return ip6_addr_string(buf, end, ptr, spec, fmt);
> > case '4':
> > return ip4_addr_string(buf, end, ptr, spec, fmt);
> >+ case 'g':
> >+ {
> >+ const struct sockaddr *sa = ptr;
> >+
> >+ if (sa->sa_family == AF_INET6) {
> >+ ptr = &((struct sockaddr_in6 *) sa)->sin6_addr;
> >+ return ip6_addr_string(buf, end, ptr, spec, fmt);
> >+ } else {
> >+ ptr = &((struct sockaddr_in *) sa)->sin_addr.s_addr;
> >+ return ip4_addr_string(buf, end, ptr, spec, fmt);
> >+ }
> >+ }
> > }
> > break;
> > case 'U':
> >@@ -1370,6 +1382,8 @@ qualifier:
> > * %pI6 print an IPv6 address with colons
> > * %pi6 print an IPv6 address without colons
> > * %pI6c print an IPv6 address as specified by RFC 5952
> >+ * %pIg depending on sa_family of 'struct sockaddr *' switch to %pI6/%pI4
> >+ * %pig depending on sa_family of 'struct sockaddr *' switch to %pi6/%pi4
> > * %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper
> > * case.
> > * %*ph[CDN] a variable-length hex string with a separator (supports up to 64
> >
>
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