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Date: Wed, 19 Aug 2009 10:26:49 -0400
From: Chuck Lever <chuck.lever@...cle.com>
To: Joe Perches <joe@...ches.com>
Cc: jens@...one.net, brian.haley@...com,
David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] lib/vsprintf.c: Add struct sockaddr * "%pN<foo>" output
On Aug 16, 2009, at 12:10 AM, Joe Perches wrote:
> Hi Chuck.
>
> Here's a tentative patch that adds that facility you wanted in
> this thread.
> http://kerneltrap.org/mailarchive/linux-netdev/2008/11/25/4231684
>
> This patch is on top of this patch:
> http://marc.info/?l=linux-netdev&m=125034992003220&w=2
>
> I'm not sure it's great or even useful, but just for discussion.
I think having at least a generic socket address formatter would be
very helpful. The kernel RPC code can use that immediately for
generating debugging messages, generating "universal
addresses" (patches already accepted for 2.6.32) and for generating
presentation addresses to pass to user space (lockd does this now).
> Use style:
> * - 'N' For network socket (sockaddr) pointers
> * if sa_family is IPv4, output is %pI4; if IPv6, output is %pI6c
> * May be used with any combination of additional specifiers
> below
> * 'p' decimal socket port number for IPv[46]: ":12345"
> * 'f' decimal flowinfo for IPv6: "/123456789"
> * 's' decimal scope_id number for IPv6: "%1234567890"
> * so %pNp will print if IPv4 "1.2.3.4:1234", if IPv6:
> "1::c0a8:a:1234"
>
> I think using ":" as the separator for the port number, while common,
> and already frequently used in kernel source (see bullet 2 in):
> http://www.ietf.org/id/draft-kawamura-ipv6-text-representation-03.txt
> "Section 6: Notes on Combining IPv6 Addresses with Port Numbers".
> is not good for readability.
>
> Perhaps this style should be changed to the "[ipv6]:port" described
> in the draft above.
I agree that the port number convention is tricky, and some kernel
areas handle it differently than others. Perhaps having a separate
family-agnostic formatter for printing the port number (or scope ID,
etc.) might allow greatest flexibility.
The RPC code, for example, displays port numbers in decimal and in
"hi.lo" format (the high byte is printed in decimal, then the low byte
is printed in decimal. The two values are separated by a dot. For
example, port 2049 is displayed as "8.1").
> cheers, Joe
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 9b79536..b3cbc38 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -791,6 +791,90 @@ static char *ip4_addr_string(char *buf, char
> *end, const u8 *addr,
> return string(buf, end, ip4_addr, spec);
> }
>
> +static char *u32_dec_val(char *p, u32 val)
> +{
> + char temp[9];
> + int digits;
> + u32 hi_val = val / 100000;
> + char *pos;
> + pos = put_dec_trunc(temp, val%100000);
> + if (hi_val)
> + pos = put_dec_trunc(pos, hi_val);
> + digits = pos - temp;
> + /* reverse the digits in temp */
> + while (digits--)
> + *p++ = temp[digits];
> + return p;
> +}
> +
> +static char *socket_addr_string(char *buf, char *end,
> + const struct sockaddr *sa,
> + struct printf_spec spec, const char *fmt)
> +{
> + char addr[sizeof("xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:255.255.255.255") +
> + sizeof(":12345") +
> + sizeof("%1234567890") +
> + sizeof("/123456789")];
> + char *p;
> + struct sockaddr_in *sa4 = (struct sockaddr_in *)sa;
> + struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)sa;
> +
> + switch (sa->sa_family) {
> + case AF_INET:
> + p = ip4_string(addr, (const u8 *)&sa4->sin_addr.s_addr, false);
> + break;
> + case AF_INET6:
> + p = ip6_compressed_string(addr, &sa6->sin6_addr);
> + break;
> + default: {
> + struct printf_spec num_spec = {
> + .base = 16,
> + .precision = -1,
> + .field_width = 2 * sizeof(void *),
> + .flags = SPECIAL | SMALL | ZEROPAD,
> + };
> +
> + p = strcpy(addr, "Bad socket address: ")
> + + sizeof("Bad socket address: ");
> + p = number(p, addr + sizeof(addr), (unsigned long)sa, num_spec);
> + break;
> + }
> + }
> +
> + while (isalpha(*++fmt)) {
> + switch (*fmt) {
> + case 'p':
> + *p++ = ':';
> + switch (sa->sa_family) {
> + case AF_INET:
> + p = u32_dec_val(p,ntohs(sa4->sin_port));
> + break;
> + case AF_INET6:
> + p = u32_dec_val(p,ntohs(sa6->sin6_port));
> + break;
> + }
> + break;
> + case 's':
> + *p++ = '%';
> + switch (sa->sa_family) {
> + case AF_INET6:
> + p = u32_dec_val(p, sa6->sin6_scope_id);
> + }
> + break;
> + case 'f':
> + *p++ = '/';
> + switch (sa->sa_family) {
> + case AF_INET6:
> + p = u32_dec_val(p, ntohl(sa6->sin6_flowinfo &
> + IPV6_FLOWINFO_MASK));
> + }
> + break;
> + }
> + }
> + *p = '\0';
> + return string(buf, end, addr, spec);
> +}
> +
> /*
> * Show a '%p' thing. A kernel extension is that the '%p' is followed
> * by an extra set of alphanumeric characters that are extended format
> @@ -814,6 +898,13 @@ static char *ip4_addr_string(char *buf, char
> *end, const u8 *addr,
> * IPv4 uses dot-separated decimal with leading 0's
> (010.123.045.006)
> * - 'I6c' for IPv6 addresses printed as specified by
> * http://www.ietf.org/id/draft-kawamura-ipv6-text-representation-03.txt
> + * - 'N' For network socket (sockaddr) pointers
> + * if sa_family is IPv4, output is %pI4; if IPv6, output is
> %pI6c
> + * May be used with any combination of additional specifiers
> below
> + * 'p' decimal socket port number for IPv[46]: ":12345"
> + * 'f' decimal flowinfo for IPv6: "/123456789"
> + * 's' decimal scope_id number for IPv6: "%1234567890"
> + * so %pNp will print if IPv4 "1.2.3.4:1234", if IPv6:
> "1::c0a8:a:1234"
> * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
> * function pointers are really function descriptors, which contain a
> * pointer to the real address.
> @@ -852,7 +943,10 @@ static char *pointer(const char *fmt, char
> *buf, char *end, void *ptr,
> return ip4_addr_string(buf, end, ptr, spec, fmt);
> }
> break;
> + case 'N':
> + return socket_addr_string(buf, end, ptr, spec, fmt);
> }
> +
> spec.flags |= SMALL;
> if (spec.field_width == -1) {
> spec.field_width = 2*sizeof(void *);
>
>
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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