Date: Thu, 23 Jun 2011 05:23:57 -0500
getaddrinfo() and gethostbyname() use error codes to describe their
errors. Pass that error code back to the caller when dns_resolve()
fails and the RESOLVE_FAIL_QUIETLY flag is set, so callers can save
the diagnosis and print it later:
int saved_rerrno = dns_resolve(...);
...
if (saved_rerrno)
die("resolver failed: %s", dns_strerror(saved_rerrno));
In the ipv4 codepath, we assume that h_errno is never 0 on error.
POSIX.1-2004 does not specify whether 0 is a valid value for h_errno,
but luckily common practice is for h_errno to be a strictly positive
integer (HOST_NOT_FOUND = 1, NO_DATA = 2, NO_RECOVERY = 3, or
TRY_AGAIN = 4). If gethostbyname errors out with h_errno == 0 on some
platform, just let git die with a message indicating a BUG so the bad
assumption can be corrected.
Signed-off-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
---
This makes saving up errors from a host resolution failure as in
v1.7.7-rc0~40^2 (connect: only log if all attempts failed, 2011-08-01)
possible. By the way, this series is currently against "maint" for no
particular reason and presumably it would conflict with that patch. ;-)
I'll be happy to rebase against "master" some time soon.
dns-ipv4.c | 7 +++++--
dns-ipv4.h | 5 +++++
dns-ipv6.c | 2 +-
dns-ipv6.h | 1 +
4 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/dns-ipv4.c b/dns-ipv4.c
index 911a8569..8820c9e8 100644
--- a/dns-ipv4.c
+++ b/dns-ipv4.c
@@ -9,8 +9,11 @@ int dns_resolve(const char *host, const char *port, int flags,
unsigned int nport;
he = gethostbyname(host);
- if (!he && (flags & RESOLVE_FAIL_QUIETLY))
- return -1;
+ if (!he && (flags & RESOLVE_FAIL_QUIETLY)) {
+ if (!h_errno)
+ die("BUG: gethostbyname failed but h_errno == 0");
+ return h_errno;
+ }
if (!he)
die("Unable to look up %s (%s)", host, hstrerror(h_errno));
diff --git a/dns-ipv4.h b/dns-ipv4.h
index c5f1778f..6f70d639 100644
--- a/dns-ipv4.h
+++ b/dns-ipv4.h
@@ -18,6 +18,10 @@ typedef struct ipv4_address resolved_address;
enum {
RESOLVE_CANONNAME = 1,
+ /*
+ * Quietly return an error code instead of exiting on error.
+ * Callers can use dns_strerror() to get an error string.
+ */
RESOLVE_FAIL_QUIETLY = 2
};
extern int dns_resolve(const char *host, const char *port, int flags,
@@ -63,6 +67,7 @@ static inline int dns_fill_sockaddr_(char *ap,
#define dns_addrlen(addr, ai) sizeof((addr).sa)
#define dns_canonname(addr, ai) ((ai).he->h_name)
+#define dns_strerror(n) hstrerror(n)
#define dns_free(ai) do { /* nothing */ } while (0)
#endif
diff --git a/dns-ipv6.c b/dns-ipv6.c
index f2325681..0b0e0602 100644
--- a/dns-ipv6.c
+++ b/dns-ipv6.c
@@ -41,7 +41,7 @@ int dns_resolve(const char *host, const char *port, int flags,
gai = getaddrinfo(host, port, &hints, res);
if (gai && (flags & RESOLVE_FAIL_QUIETLY))
- return -1;
+ return gai;
if (gai)
die("Unable to look up %s (port %s) (%s)", host, port, gai_strerror(gai));
diff --git a/dns-ipv6.h b/dns-ipv6.h
index 16bf84b5..4211c9e2 100644
--- a/dns-ipv6.h
+++ b/dns-ipv6.h
@@ -26,6 +26,7 @@ extern char *dns_ip_address(const resolved_address *i,
#define dns_addrlen(i, ai) ((i)->ai_addrlen)
#define dns_canonname(i, ai) ((i)->ai_canonname)
+#define dns_strerror(gai) gai_strerror(gai)
#define dns_free(ai) freeaddrinfo(ai)
#endif
--
1.7.9.2
--
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